KR20140093618A - Composition for etching mask and method of forming pattern - Google Patents

Abstract

A printing characteristic is improved when a composition for an etching mask is printed on a substrate for a solar cell. A composition for an etching mask of a substrate for a solar cell according to the present invention is non-photosensitive and includes 100 parts by mass of novolac resin (A), 20-100 parts by mass of SiO2 particles (B), and a solvent (C).

Description

TECHNICAL FIELD [0001] The present invention relates to a composition for an etching mask,

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

In the solar cell manufacturing process, a mask material is used when the substrate is partially etched. Conventionally, a photoresist has been used in this process, but application of a print type resist has been studied for the purpose of reducing the number of process steps at present. A strong acid such as hydrofluoric acid, nitric acid, or the like is used as an etching solution for etching the substrate for a solar cell. For this reason, it is required that the properties required for a print type resist are capable of forming an acid resistance to an etching solution at the time of etching and a pattern according to a printing method.

Japanese Patent Application Laid-Open No. 9-293888

There has been room for improvement in that conventional print type resists can sufficiently reproduce the print design and form a good pattern while ensuring sufficient acid resistance. In addition, there was room for improvement in the printing stability upon continuous printing.

The present invention has been made in view of these problems, and an object of the present invention is to provide a technique capable of improving the printability when a composition for an etching mask is printed on a solar cell substrate.

An embodiment according to the present invention is a composition for an etching mask. The composition for an etching mask is a composition for an etching mask of a substrate for a non-photosensitive solar cell comprising 100 parts by mass of a novolac resin (A), 20 to 100 parts by mass of a SiO ₂ particle (B), and a solvent (C).

According to the above composition for an etching mask of the present invention, the printing property upon printing on a solar cell substrate can be improved.

In the above composition for an etching mask, 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 silicone-based, acrylic-based or fluorine-based surfactant (D) may be further provided.

Another aspect 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 using a composition for an etching mask of a substrate for a solar cell according to any one of the above modes, a step of baking the mask pattern, a step of etching the substrate, A step of transferring the pattern, and a step of removing the mask pattern.

According to the present invention, it is possible to improve the acid resistance and printability when a composition for an etching mask is printed on a solar cell substrate.

1 (A) to 1 (C) are schematic sectional views showing a pattern forming process for 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 substrate for a solar cell is partially etched.

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

Examples of the novolac resin (A) include novolac resins obtained by reacting phenols exemplified below with aldehydes exemplified below in the presence of an acidic catalyst such as hydrochloric acid, sulfuric acid, formic acid, oxalic acid, para-toluenesulfonic acid and the like.

Examples of the phenols include phenols such as cresols such as m-cresol, p-cresol and o-cresol; alicyclic compounds such as 2,3-xylenol, 2,5-xylenol, 3,5- Xylenol, and the like; xylenols such as m-ethylphenol, p-ethylphenol, o-ethylphenol, 2,3,5-trimethylphenol, 2,3,5-triethylphenol, 4- Alkylphenols such as phenol, 3-tert-butylphenol, 2-tert-butylphenol, 2-tert-butyl-4-methylphenol and 2- Alkoxyphenols such as methoxyphenol, p-ethoxyphenol, m-ethoxyphenol, p-propoxyphenol and m-propoxyphenol, o-isopropenylphenol, p- Isopropenylphenols such as 4-isopropenylphenol and 2-ethyl-4-isopropenylphenol, arylphenols such as phenylphenol, 4,4'-dihydroxybiphenyl, bisphenol A, resorcinol, hydroquinone , Polyhydroxyphenols such as pyrogenic rolls, and the like. These may be used alone or in combination of two or more. Of these phenols, m-cresol and p-cresol are particularly preferable.

Examples of aldehydes include aldehydes such as formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, butylaldehyde, trimethylacetaldehyde, acrolein, crotonaldehyde, cyclohexanaldehyde, furfural, furyl acrolein, benzaldehyde, terephthalaldehyde, Methylbenzaldehyde, p-methylbenzaldehyde, p-methylbenzaldehyde, o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, o-methylbenzaldehyde, - chlorobenzaldehyde, m-chlorobenzaldehyde, p-chlorobenzaldehyde, cinnamaldehyde and the like. These may be used alone or in combination of two or more. Of these aldehydes, formaldehyde is preferred because of their ease of availability.

The novolak resin (A) may be composed of one kind of novolac resin or two or more kinds of novolak resins. When the novolak resin (A) is composed of two or more novolac resins, the Mw of each novolac resin is not particularly limited, but it is preferable that the novolak resin (A) is prepared so that the Mw is 1000 to 100000 as a whole . The novolak resin (A) is preferably contained in an amount of 20 to 80 mass%, more preferably 60 to 80 mass%, of the components (solid components) other than the solvent (C) in the composition for an etching mask.

As the properties common to the novolac resin (A) described above, those having excellent acid resistance can be cited.

The content of the SiO ₂ particles (B) is 20 to 100 parts by mass with respect to 100 parts by mass of the novolak resin (A). That the content of SiO ₂ particles (B) to obtain sufficient printability is less than 20 parts by mass based on 100 parts by weight of novolak resin (A) it becomes difficult. On the other hand, if the content of the SiO ₂ particles (B) is more than 100 parts by mass based on 100 parts by mass of the novolak resin (A), it becomes difficult to secure sufficient acid resistance. The average particle diameter of the SiO ₂ particles (B) is preferably 7 nm to 30 nm. If the average particle diameter of the SiO ₂ particles (B) is less than 7 nm, the particles tend to aggregate. On the other hand, if the average particle diameter of the SiO ₂ particles (B) is larger than 30 nm, the thickening and the chirp-trophic properties are lowered. The SiO ₂ particles (B) are preferably hydrophilic. The term " hydrophilic " as used herein refers to having a hydroxyl group (OH group) on the particle surface. The degree of printing can be increased because the SiO ₂ particles (B) are hydrophilic.

The content of the solvent (C) is preferably 30 to 70% by mass based on the entire composition for an 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 Diethyleneglycol monobutyl ether acetate, glycerin, benzyl alcohol, 3-methyl-3-methoxybutyl acetate, 3-ethyl-3-methoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate Methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate, Acetate, dihexyl ether, benzyl acetate, ethyl benzoate, diethyl maleate,? -Butyrolactone, terpineol and the like. These may be used alone or in combination of two or more.

The composition for an etching mask according to the embodiment may contain a solvent other than the above-mentioned solvent (C1). However, the content of the solvent (C1) in the whole solvent is 70% by mass or more, more preferably 90% by mass or more.

Examples of the solvent other than the solvent C1 (solvent (C2) having a boiling point of less than 190 deg. C) include ketones such as cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone and 2-heptanone; 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, etc. Other examples include butyl acetate, ethyl acetoacetate, Butyl lactate, diethyl oxalate and the like. Among these, propylene glycol monomethyl ether acetate, 2-heptanone, and butyl acetate are preferable.

The composition for an etching mask according to the embodiment may further comprise a silicone-based, acrylic-based or fluorine-based surfactant (D).

Examples of the silicone surfactant (D) include BYK-310 (a big chemical agent) mainly composed of polyester-modified polydimethylsiloxane, BYK-323 (a big chemical agent) having an aralkyl-modified polymethylalkylsiloxane as a main component, polyether- BYK-SILCLEAN3720 (manufactured by Big Chem) containing hydroxyl group-containing polydimethylsiloxane as a main component and KF-353 (manufactured by Shin-Etsu Chemical Co., Ltd.) having polyether-modified methylpolysiloxane as a main component. Examples of the acrylic surfactant (D) include BYK-354 (Big Chemie). Examples of the fluorine surfactant (D) include KL-600 (manufactured by Kyowa Chemical Industry Co., Ltd.). Among these, a silicone surfactant is preferable, and a polydimethylsiloxane surfactant is preferable. The amount of the surfactant (D) to be added is preferably 0.001 mass% to 1.0 mass%, more preferably 0.01 mass% to 0.1 mass%, based on the entire composition for an etching mask.

The above-described composition for an etching mask can improve resistance to an etching solution in the state that it is formed as a mask on a solar cell substrate by printing by including a novolak resin (A) having excellent acid resistance as a resin component. In addition, by containing 20 to 100 parts by mass of the SiO ₂ particles (B) relative to 100 parts by mass of the novolak resin (A), the printing property can be improved. Further, the solvent (C), particularly the solvent (C1) having a boiling point of 190 ° C or higher, is contained to suppress the drying of the composition (ink) for etching mask at the time of printing to improve reprintability (print stability) Can be improved.

Further, the composition for an etching mask contains the surfactant (D), so that the width of the actually printed pattern becomes larger with respect to the print pattern width set when the composition for etching mask is printed on the substrate for solar cell, Can be suppressed.

(Pattern forming method)

Also, a silicon substrate or a copper, nickel, a is a nitride film such as oxide film or SiN on the metal layer on a metal substrate or a silicon substrate such as aluminum, SiO _2, etc. is deposited solar cell substrate as shown in FIG. 1 (A) ( 10) Using the above composition for an etching mask, a mask (not shown) is formed by a printing method such as a screen printing method, an inkjet printing method, a roll coat printing method, a convex plate printing method, an intaglio printing method, Pattern 20 is formed. Further, before the mask pattern 20 is formed, the substrate may be pretreated as necessary. The pretreatment furnace may include a step of forming a liquid-repellent layer, for example, a process described in JP-A-2009-253145. Subsequently, the mask pattern 20 is baked by heating the mask pattern 20. The heating conditions are appropriately set according to the composition of the composition for an etching mask and the film thickness of the mask pattern 20, for example, but it is, for example, 200 占 폚 for 3 minutes.

Subsequently, as shown in Fig. 1 (B), the solar cell substrate exposed in 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, (Exposed part) is etched to transfer the mask pattern.

Subsequently, as shown in Fig. 1 (C), after the etching process, the mask pattern 20 is removed. Examples of the removal method include a method in which the substrate is immersed in an aqueous alkali solution, an organic solvent, a commercially available peeling solution at room temperature for 5 minutes to 10 minutes, and then peeled. Examples of the aqueous alkali solution include an aqueous solution of sodium hydroxide and an aqueous solution of tetramethylammonium hydroxide (TMAH). Examples of the organic solvent include propylene glycol monomethyl ether acetate (PGMEA), dimethyl sulfoxide (DMSO), and the like. As a commercially available peeling solution, an organic solvent type HAKURI 105 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) or the like can be used. As a result, a pattern in which convex portions along the mask pattern 20 are transferred onto the solar cell substrate 10 can be obtained. Examples of the function of the convex portion formed on the solar cell substrate include an electrode and a diffusion layer.

Through the above steps, convex portions of a predetermined pattern can be formed on the solar cell substrate. The composition for an etching mask described above is excellent in acid resistance and pattern formation accuracy, so that a desired pattern can be formed on a solar cell substrate to a satisfactory extent. In addition, since the pattern is formed on the substrate for the solar cell by the printing method without passing through a complicated process such as the photolithography method, the manufacturing process of the solar cell can be simplified and the manufacturing cost of the solar cell can be further reduced.

Example

Hereinafter, embodiments of the present invention will be described, but these embodiments are only examples for explaining the present invention very suitably, and are not intended to limit the present invention at all.

(Examples 1-11 and Comparative Example  1-12)

Table 1 shows the compositions of the composition for etching masks of Example 1-11 and Comparative Example 1-12. The novolak resin 1 and novolac resin 2 used in the composition for etching mask of Example 1-11 and Comparative Example 1-12 had a mass average molecular weight of 12,000 (m / p = 60/40) and a mass average molecular weight of 2100 (m / p = 36/64). Table 2 shows the details of the fillers used in Examples 1-11 and 5-12. Table 3 shows the details of the surfactants used in Examples 1, 2, 4-11 and Comparative Examples 3-12. An ink comprising the compositions for etching masks of Example 1-11 and Comparative Example 1-12 was produced by combining the components shown in Table 1.

In Table 2, filler 2 and filler 3 have different specific gravity. Three pillars are easy to handle because of their large weight.

(Evaluation of printability of screen printing)

Each of the produced inks was printed on a silicon substrate by a screen printing method, and three patterns of widths of 100 占 퐉, 150 占 퐉 and 200 占 퐉 were formed as print design widths. The formed pattern was dried on a hot plate at 200 캜 for 3 minutes. The finish line width of the obtained pattern was measured to confirm the printability. The results of printability are classified as follows. Table 4 shows the results obtained for the printability.

(Good): Printing blurring of all patterns is 20 占 퐉 or less

○ (Possible): Two patterns with printing blur of 20 μm or less

× (bad): 1 or 0 pattern with printing blur of 20 μm or less

The printing blurring is calculated by the following formula.

Print spread = Finish line width - Print design width

(Chisel Trophy castle  evaluation)

The viscosity index of each ink was measured by using an E-type viscometer (synchronous industry, RE550 type viscometer), and the viscosity index was calculated based on the following formula.

Viscosity Index = viscosity at 1 rpm / viscosity at 15 rpm

The resulting viscosity index was classified as follows and the chimney trophicity was evaluated. Table 4 shows the results obtained for the chisel trophic properties.

◎ (Good): Viscosity index 3.0 or higher

○ (Possible): Viscosity index 2.0 or more and less than 3.0

× (poor): Viscosity index less than 2.0

As shown in Table 4, each of the inks of Comparative Examples 1-12 had poor printability and bulky tropism. On the other hand, it was confirmed that the inks of Examples 1-14 had both printability and rumen tropic properties of ◯ (possible) or more. Particularly, in comparison between Example 2 and Example 3, it was confirmed that the printing property was further improved by adding a surfactant. Comparing Example 1 and Example 6, it was confirmed that the smaller the particle diameter of the filler, the more excellent the printing property and the chirp trophicity. Comparing Example 1 and Example 7, it was confirmed that the printability and the chirp trophicity were further improved because the filler was hydrophilic.

(Evaluation of printing stability of screen printing)

For each of the inks of Examples 1, 8-10, and 12-14 described above, screen printing was performed for 7 shots continuously, and printing stability was confirmed. Table 5 shows the number of shots that were able to be printed without printing impression on the results of the printing stability. In Examples 9 and 10, the boiling point of the solvent is an average boiling point determined from the boiling point and mixing ratio of the two kinds of solvents.

From Table 5, it was confirmed that the printing stability was improved when the solvent had a boiling point (including an average boiling point) of 190 ° C or higher. In Examples 1 and 8-10, there was no print smear on the print patterns from the 1st shot to the 7th shot, and in Examples 1, 8, and 9 in particular, the smoothness of the surface of the print pattern from the 1st shot to the 7th shot .

( Acid resistance  evaluation)

Each ink of Example 1-11 was printed on a silicon substrate by a screen printing method to form a pattern having a width of 100 mu m and a width of 200 mu m. The formed pattern was dried on a hot plate at 200 캜 for 3 minutes. In order to confirm the acid resistance of the formed pattern, it was immersed in a 5% aqueous solution of hydrofluoric acid (condition 1) or a 10% aqueous solution of sulfuric acid (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 Condition 1 and Condition 2, and peeling of the pattern and generation of cracks did not occur.

10 Substrate for solar cell,
20 mask pattern

Claims (5)

100 parts by mass of the novolac resin (A)
20 to 100 parts by mass of the SiO ₂ particles (B)
Solvent (C)
Wherein the photoresist composition is a photoresist composition. The method according to claim 1,
Wherein the solvent (C) comprises a solvent (C1) having a boiling point of 190 ° C or higher. The method according to claim 1 or 2,
SiO ₂ particles (B) the hydrophilic composition of the etching mask. The method according to any one of claims 1 to 3,
A composition for a mask, further comprising a silicon-based, acrylic-based or fluorine-based surfactant (D). A step of forming a mask pattern by a printing method using a composition for an etching mask of a substrate for a solar cell according to any one of claims 1 to 4 on a substrate,
A step of baking the mask pattern;
A step of etching the substrate to transfer the mask pattern,
Step of removing mask pattern
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