JP6447493B2 - Barrier layer forming composition, semiconductor substrate with barrier layer, method for producing solar cell substrate, and method for producing solar cell element - Google Patents

Description

  The present invention relates to a barrier layer forming composition, a semiconductor substrate with a barrier layer, a method for manufacturing a solar cell substrate, and a method for manufacturing a solar cell element.

The manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate having a texture structure formed on the light-receiving surface is prepared so as to promote the light confinement effect and increase the efficiency, and then in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen, 800 Several tens of minutes of treatment is performed at a temperature of from 900 to 900 ° C. to uniformly form an n-type diffusion layer on the surface of the p-type silicon substrate. Then, after applying an electrode paste such as silver (Ag) on the light receiving surface and an electrode paste such as aluminum (Al) on the back side, a solar cell element was obtained by heat treatment (firing).

However, since sunlight does not enter directly under the electrode on the light receiving surface side, power is not generated in that portion. Therefore, a back electrode type solar cell having no electrode on the light receiving surface, having an n ⁺ type diffusion layer and a p ⁺ type diffusion layer on the back surface, and having an n electrode and a p electrode on each diffusion layer has been developed ( For example, refer to Unexamined-Japanese-Patent No. 2011-507246).

A method of forming such a back electrode type solar cell will be described. A barrier layer is formed on the entire light receiving surface and back surface of the n-type silicon substrate. Here, the barrier layer has a function of suppressing the diffusion of the dopant into the silicon substrate. Next, a part of the barrier layer on the back surface of the silicon substrate is removed to form an opening. Then, when p-type dopant is diffused from the opening of the barrier layer to the back surface of the silicon substrate, a p ⁺ -type diffusion layer is formed in a region corresponding to the opening. Next, after all the barrier layer on the back surface of the silicon substrate is removed, a barrier layer is formed again on the entire back surface of the silicon substrate. Then, a part of the barrier layer in a region different from the region where the p ⁺ -type diffusion layer is formed is removed to form an opening, and an n-type dopant is diffused from the opening to the back surface of the silicon substrate. ^{A +} type diffusion layer is formed. Subsequently, by removing all the barrier layer on the back surface of the silicon substrate, a p ⁺ -type diffusion layer and an n ⁺ -type diffusion layer are formed on the back surface. Furthermore, a back electrode type solar cell is completed by forming a texture structure, an antireflection layer, a passivation layer, an electrode, and the like.

As the barrier layer, a method using an oxide film formed on the surface of a silicon substrate by a thermal oxidation method has been proposed (see, for example, JP-A-2002-329880). On the other hand, a method for forming a barrier layer using a masking paste containing a SiO ₂ precursor has also been proposed (see, for example, Japanese Patent Application Laid-Open No. 2011-119341).

However, the method of generating an oxide film on the surface of a silicon substrate by the thermal oxidation method described in the aforementioned Japanese Patent Application Laid-Open No. 2002-329880 has a problem that the manufacturing cost is high because the throughput is long.
Further, described in JP-A-2011-119341, in the method of using the masking paste containing SiO ₂ precursor, assumes a paste of a low viscosity of 0.1mPa · s~30mPa · s, a screen printing method It was difficult to apply a thick mask layer. Therefore, in this method, there is a problem that the diffusion of the dopant cannot be sufficiently prevented.

  The present invention has been made in view of the above conventional problems, and a barrier layer forming composition capable of sufficiently preventing the diffusion of a donor element or an acceptor element into a semiconductor substrate, and a barrier layer using the same It is an object of the present invention to provide a method for manufacturing an attached semiconductor substrate, a solar cell substrate, and a solar cell element.

Specific means for solving the above problems are as follows.
<1> At least one silicon-containing compound selected from the group consisting of at least one alkoxysilane represented by the following general formula 1, polysilazane, and a siloxane resin obtained by hydrolysis and condensation polymerization of the alkoxysilane, and an organic binder And a dispersion medium, and a viscosity at 25 ° C. of 1 Pa · s to 100 Pa · s.

(R ¹ ) _4-n Si (OR ² ) _n ... General formula 1

In General Formula 1, R ¹ and R ² each independently represents an aliphatic hydrocarbon group having 1 to 6 carbon atoms or an aromatic hydrocarbon group, and n represents an integer of 1 to 4. When two or more R ¹ or R ² are contained, each R ¹ or each R ² may be the same or different.

<2> The composition for forming a barrier layer according to <1>, wherein the content of the silicon-containing compound is 1% by mass to 18% by mass in terms of SiO ₂ .

<3> The composition for forming a barrier layer according to <1>, wherein the content of the silicon-containing compound is 5% by mass to 16% by mass in terms of SiO ₂ .

<4> The composition for forming a barrier layer according to <1>, wherein the content of the silicon-containing compound is 6% by mass to 13% by mass in terms of SiO ₂ .

<5> The composition for forming a barrier layer according to any one of <1> to <4>, wherein the organic binder includes at least one selected from the group consisting of a cellulose derivative, an acrylic resin, and an alkyd resin. .

<6> The composition for forming a barrier layer according to any one of <1> to <5>, wherein the organic binder includes ethyl cellulose.

<7> The dispersion medium according to any one of <1> to <6>, wherein the dispersion medium includes at least one selected from the group consisting of water, an alcohol solvent, an ether solvent, a glycol monoether solvent, and a terpene solvent. A barrier layer forming composition.

<8> For forming a barrier layer according to any one of <1> to <6>, wherein the dispersion medium includes at least one selected from the group consisting of terpineol, butyl carbitol, and butyl carbitol acetate. Composition.

<9> The composition for forming a barrier layer according to any one of <1> to <8>, wherein the viscosity at 25 ° C. is 10 Pa · s to 80 Pa · s.

<10> a semiconductor substrate;
Wherein the barrier layer is a dried body of the semi conductor is applied onto the substrate, the <1> to barrier layer forming composition according to any one of <9>,
A semiconductor substrate with a barrier layer.

<11> A step of applying the barrier layer forming composition according to any one of <1> to <9> onto a semiconductor substrate to form a patterned barrier layer;
A step of diffusing a donor element or an acceptor element in a portion of the semiconductor substrate where the barrier layer is not formed, and partially forming a diffusion layer in the semiconductor substrate. Production method.

<12> The method for producing a solar cell substrate according to <11>, wherein the method for applying the barrier layer-forming composition to the semiconductor substrate is a screen printing method.

<13> A method for producing a solar cell element, comprising a step of forming an electrode on a diffusion layer of a solar cell substrate obtained by the production method according to <11> or <12>.

  According to the present invention, a composition for forming a barrier layer that can sufficiently prevent the diffusion of a donor element or an acceptor element into a semiconductor substrate, a semiconductor substrate with a barrier layer using the composition, a method for producing a substrate for a solar cell, And the manufacturing method of a solar cell element can be provided.

It is sectional drawing which shows notionally an example of the manufacturing process of the board | substrate for solar cells of this invention, and a solar cell element.

  First, the composition for forming a barrier layer of the present invention will be described, and then a semiconductor substrate with a barrier layer using the composition for forming a barrier layer, a method for manufacturing a solar cell substrate, and a method for manufacturing a solar cell element will be described.

  In this specification, the term “process” is not limited to an independent process, and even if it cannot be clearly distinguished from other processes, the term “process” is used if the intended action of the process is achieved. included. In addition, in this specification, “to” indicates a range including numerical values described before and after that as a minimum value and a maximum value, respectively. Further, in this specification, the amount of each component in the composition is the sum of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. Means quantity. In this specification, the term “layer” includes a configuration formed in a part in addition to a configuration formed in the entire surface when observed as a plan view.

In addition, the donor element or the acceptor element may be referred to as a dopant.
The barrier layer in the present invention includes not only the case where it is formed on the entire surface when the semiconductor substrate is observed as a plan view but also the case where it is formed on a part thereof.

<Barrier layer forming composition>
The composition for forming a barrier layer of the present invention is at least one selected from the group consisting of at least one alkoxysilane represented by the following general formula 1, polysilazane, and a siloxane resin obtained by hydrolysis and condensation polymerization of the alkoxysilane. A silicon-containing compound, an organic binder, and a dispersion medium. The composition for forming a barrier layer of the present invention has a viscosity at 25 ° C. of 1 Pa · s to 100 Pa · s.

(R ¹ ) _4-n Si (OR ² ) _n ... General formula 1

In General Formula 1, R ¹ and R ² each independently represents an aliphatic hydrocarbon group having 1 to 6 carbon atoms or an aromatic hydrocarbon group, and n represents an integer of 1 to 4. When two or more R ¹ or R ² are contained, each R ¹ or each R ² may be the same or different.

Hereinafter, selected from the group consisting of at least one alkoxysilane represented by the general formula (R ¹ ) _4-n Si (OR ² ) _n , polysilazane, and a siloxane resin obtained by hydrolysis and condensation polymerization of the alkoxysilane. At least one silicon-containing compound is also referred to as a “specific silicon-containing compound”. A siloxane compound refers to a compound having a Si—O—Si bond.

  The composition for forming a barrier layer of the present invention inhibits diffusion of a donor element or an acceptor element, which is a dopant, into a semiconductor substrate. Therefore, by forming a barrier layer using the barrier layer forming composition of the present invention in a region where the donor element or the acceptor element is not desired to be diffused in the semiconductor substrate, the donor element and the acceptor element are diffused in the region. It can be sufficiently prevented. Therefore, it is possible to selectively form a doping region in the semiconductor substrate. The reason for this can be considered as follows.

  A specific silicon-containing compound is included in the composition for forming a barrier layer together with an organic binder and a dispersion medium that can be adjusted to a specific viscosity, and this barrier layer-forming composition is applied to a semiconductor substrate by a screen printing method and heat-treated. The formed barrier layer has a high barrier performance. This is because a thick barrier layer can be easily formed by the screen printing method. Moreover, the barrier layer which a crack does not generate | occur | produce easily can be formed by using the composition for barrier layer formation which adjusted the viscosity to 1 Pa * s-100 Pa * s. This barrier layer can effectively prevent high barrier performance, that is, dopant diffusion.

  The specific silicon-containing compound is at least one selected from the group consisting of at least one alkoxysilane represented by the following general formula 1, polysilazane, and a siloxane resin obtained by hydrolysis and condensation polymerization of the alkoxysilane.

(R ¹ ) _4-n Si (OR ² ) _n General formula 1

In General Formula 1, R ¹ and R ² are each independently an aliphatic hydrocarbon group or an aromatic hydrocarbon group having 1 to 6 carbon atoms, and n is an integer of 1 to 4. When two or more R ¹ or R ² are contained, each R ¹ or each R ² may be the same or different.

R ¹ and R ² are each independently an alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, isohexyl, phenyl group, alkyl halide, etc. Examples include groups.

  Specifically, as the alkoxysilane, it is preferable to use at least one selected from the group consisting of tetraethoxysilane, tetramethoxysilane, methyltrimethoxysilane, and methyltriethoxysilane, from tetraethoxysilane and tetramethoxysilane. It is more preferable to use at least one selected from the group consisting of Since tetraethoxysilane and tetramethoxysilane are rich in reactivity, a dense layer can be easily formed and a barrier layer with high barrier performance can be formed.

  Examples of the siloxane resin obtained by hydrolyzing and polymerizing alkoxysilane include compounds represented by the following general formulas 2 and 3.

Si _n O _n-1 (OCH ₃ ) _{2 (n + 1)} General formula 2
Si _n O _n-1 (OC ₂ H ₅ ) _{2 (n + 1)} general formula 3

  In General Formula 2 and General Formula 3, n independently represents an integer of 2 to 100, n is preferably 2 to 20, and n is more preferably 3 to 8. Examples of such commercially available products include methyl silicate oligomer “MKC silicate” manufactured by Mitsubishi Chemical Corporation, silicate manufactured by Tama Chemical Industry Co., Ltd. (silicate 40, silicate 45, M silicate 51, etc.), and silicate manufactured by Colcoat Co., Ltd. (methyl silicate 51). , Methyl silicate 53A, ethyl silicate 40, ethyl silicate 48), silicate oligomer such as EMS-485, methyl silicone oil such as polydimethylsiloxane, silicone oil such as methyl phenyl silicone oil, methyl hydrogen silicone oil, modified silicone oil Is mentioned.

  Further, polysilazane may be used as the specific silicon-containing compound. By using highly reactive polysilazane, a dense layer can be easily formed and a barrier layer with high barrier performance can be formed. Either inorganic or organic polysilazane may be used, and examples of the inorganic polysilazane include linear compounds having a structural unit represented by the following general formula 4.

  In general formula 4, n represents an integer.

The weight average molecular weight of the inorganic polysilazane is preferably 690 to 2000. In particular, it has 3 to 10 SiH ₃ groups in one molecule, and the element ratio by chemical analysis is Si: 59 to 61, N: 31 to 34, and H: 6.5 to 7.5 in each mass%. A certain perhydropolysilazane and a perhydropolysilazane having a polystyrene-converted average molecular weight in the range of 3,000 to 20,000 can be mentioned. In addition, the weight average molecular weight of inorganic polysilazane is converted from a calibration curve using standard polystyrene by gel permeation chromatography (GPC).

  Examples of commercially available polysilazane include “NN110” manufactured by AZ Electronic Materials, “Aquamica” manufactured by Clariant Japan, and “Hard Barrier XR” manufactured by Leeds Factory.

  In order to advance hydrolysis, water, a catalyst, etc. may be added to the composition for forming a barrier layer as necessary. Catalysts include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, boric acid, phosphoric acid, hydrofluoric acid, and formic acid, acetic acid, propionic acid, butyric acid, oleic acid, linoleic acid, salicylic acid, benzoic acid, phthalic acid, oxalic acid And organic acids such as lactic acid and succinic acid. Moreover, you may add bases, such as ammonia and an amine, as a catalyst.

Further, the content of the specific silicon-containing compound in the barrier layer forming composition is preferably 1% by mass to 18% by mass, more preferably 5% by mass to 16% by mass in terms of SiO ₂ , More preferably, it is 6 mass%-13 mass%. Within the above range, a sufficient barrier layer control effect tends to be obtained.

(Dispersion medium)
The barrier layer forming composition of the present invention contains a dispersion medium. The dispersion medium is a medium in which the specific silicon-containing compound or the organic binder is dispersed or dissolved in the composition.

Examples of the solvent include acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl n-hexyl ketone, diethyl ketone, Ketone solvents such as propyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone, diethyl ether, methyl ethyl ether, methyl-n-propyl ether, diisopropyl ether , Tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol Rudi-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol mono-n-butyl ether (also known as butyl carbitol), diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl-n -Butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di-n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl-n -Butyl ether , Triethylene glycol di-n-butyl ether, triethylene glycol methyl-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, tetraethylene glycol di -n- butyl ether, tetraethylene glycol methyl -n- Hekishiruete Le, profile propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di -n- propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether , Dipropylene glycol methyl ethyl ether , Dipropylene glycol methyl-n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, Tripropylene glycol methyl ethyl ether, tripropylene glycol methyl-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl Ethyl ether, tetrapropylene glycol methyl-n-butyl ether Ether solvent such as tetrapropylene glycol di-n-butyl ether, tetrapropylene glycol methyl-n-hexyl ether, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-acetate Butyl, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methyl pentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, cyclohexyl acetate, acetic acid Methyl cyclohexyl, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, acetic acid diethylene glycol methyl ether, acetic acid diethylene glycol monoethyl ether, acetic acid diethylene glycol mono-n-butyl ether (also known as butyl carbonate) Bitol acetate), dipropylene glycol methyl ether, dipropylene glycol ethyl ether acetate, glycol diacetate, methoxytriethylene glycol acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-oxalate n-butyl, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol Methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, γ-butyrolacto Ester solvents such as γ-valerolactone, acetonitrile, N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N , N-dimethylacetamide, aprotic polar solvents such as dimethyl sulfoxide, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, n-pentanol, isopentanol, 2-methylbutanol, sec-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-hepta Nord, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, phenol, cyclohexanol , Methylcyclohexanol, benzyl alcohol, isobornylcyclohexanol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and other alcohol solvents, ethylene Glycol monomethyl ether, ethylene glycol monoethyl ether (cellosolve), ethylene glycol monophenyl ether, di Tylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, di Glycol monoether solvents such as propylene glycol monoethyl ether and tripropylene glycol monomethyl ether, α-terpinene, α-terpineol, myrcene, allocymene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, osymene, ferlandylene Terpene solvent such as xylene, isobornylphenol, 1-isopropyl- 4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic anhydride, and p-mentenylphenol. These are used singly or in combination of two or more.

  Among these, from the viewpoint of applicability to a semiconductor substrate, the dispersion medium is preferably at least one selected from the group consisting of water, alcohol solvents, ether solvents, glycol monoether solvents and terpene solvents, water, alcohol, Cellosolve, terpineol (such as α-terpineol), diethylene glycol mono-n-butyl ether, or acetic acid diethylene glycol mono-n-butyl ether is more preferable, and at least one selected from the group consisting of terpineol, butyl carbitol, and butyl carbitol acetate is further included. preferable.

  The content of the dispersion medium in the composition for forming a barrier layer is determined in consideration of applicability and dopant concentration. For example, the content is preferably 5% by mass to 99% by mass, and more preferably 20% by mass to 95% by mass. More preferably, it is 40 mass% or more and 90 mass% or less.

(Organic binder)
The barrier layer forming composition of the present invention contains an organic binder. By containing an organic binder, the viscosity can be adjusted, and sagging of printed lines during screen printing can be suppressed.

  Examples of the organic binder include polyvinyl alcohol, polyacrylamide resin, polyvinylamide resin, polyvinylpyrrolidone resin, polyethylene oxide resin, polysulfone resin, acrylamide alkylsulfone resin, cellulose ether, carboxymethylcellulose, hydroxyethylcellulose, ethylcellulose and other cellulose derivatives, gelatin , Gelatin derivative, starch, starch derivative, sodium alginate compound, xanthan, guar gum, guar gum derivative, scleroglucan, scleroglucan derivative, tragacanth, tragacanth derivative, dextrin, dextrin derivative, (meth) acrylic acid resin, alkyl (meth) Contains amino groups such as acrylate resin, dimethylaminoethyl (meth) acrylate resin ( Data) acrylic acid ester resins, butadiene resins, styrene resins, butyral resins, and may select these copolymers as appropriate.

  Among these, the organic binder preferably contains at least one selected from the group consisting of an acrylic acid resin, an alkyd resin, and a cellulose derivative from the viewpoints of degradability and prevention of dripping when screen printed. More preferably, it contains a cellulose derivative. Examples of the cellulose derivative include ethyl cellulose, nitrocellulose, acetyl cellulose, carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, and hydroxyethyl cellulose. Among these, ethyl cellulose is preferably used. These are used singly or in combination of two or more.

  The molecular weight of the organic binder is not particularly limited, and it is desirable to adjust appropriately in view of the desired viscosity as the composition. The organic binder content in the barrier layer forming composition is preferably 0.5% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 25% by mass or less, and more preferably 3% by mass. More preferably, it is 20 mass% or less.

  In addition, as the dispersion medium and the organic binder, a dispersion medium in which an organic binder is dissolved may be used.

  In addition, the composition for barrier layer formation may use the isobornyl cyclohexanol illustrated as a solvent with the organic binder as a material replaced with an organic binder. Isobornylcyclohexanol is commercially available as “Telsolve MTPH” (Nippon Terpene Chemical Co., Ltd., trade name). Isobornylcyclohexanol has a high boiling point of 308 ° C to 318 ° C, and when it is removed from the barrier layer, it does not need to be degreased by firing like an organic binder, but must be vaporized by heating. Can do.

  When the composition for forming a barrier layer contains isobornylcyclohexanol, the content of isobornylcyclohexanol is 0.5% by mass to 85% by mass in the total mass of the composition for forming a barrier layer. Is preferable, more preferably 1% by mass to 80% by mass, and still more preferably 2% by mass to 80% by mass.

(Other ingredients)
In addition to the specific silicon-containing compound, the organic binder, and the dispersion medium, the barrier layer-forming composition includes a thickener, a wetting agent, a surfactant, an inorganic powder, a thixotrope as other components as necessary. You may contain various additives, such as an agent.

  Examples of the surfactant include nonionic surfactants, cationic surfactants, and anionic surfactants. Among these, nonionic surfactants or cationic surfactants are preferred because impurities such as heavy metals are not brought into the semiconductor device. Furthermore, silicon-containing surfactants, fluorine-containing surfactants, and organic surfactants are exemplified as nonionic surfactants, and organic surfactants are preferred because they are baked quickly during heating such as diffusion.

  Examples of the organic surfactant include an ethylene oxide-propylene oxide block copolymer, an acetylene glycol compound, and the like, and an acetylene glycol compound is more preferable because variation in resistance value of the semiconductor device is further reduced.

  Examples of the inorganic powder include powders of silicon oxide, silicon nitride, silicon carbide and the like.

  The composition for forming a barrier layer may contain a thixotropic agent. Thereby, thixotropy can be easily controlled, and a composition for forming a barrier layer for screen printing having a viscosity suitable for screen printing can be constituted. Furthermore, since thixotropy is controlled, it is possible to suppress bleeding and sagging of the printing pattern of the composition for forming a barrier layer during printing.

As thixotropic agents, polyether compounds, fatty acid amides, organic fillers, inorganic fillers, hydrogenated castor oil, urea urethane amide, bio gum, guar gum, locust bean gum, carrageenan, pectin, agar, β-glucan, tamarind seed gum, psyllium seed gum , Polyvinyl pyrrolidone, silicone-based thickening gelling agent and oil-based gelling agent (trade name: Gelol (Shin Nihon Rika Co., Ltd.), “Gelall” is a registered trademark).
The organic binder described above may also serve as a thixotropic agent. Examples of such a material include ethyl cellulose.

  The composition for forming a barrier layer of the present invention does not contaminate the semiconductor substrate, that is, from the viewpoint of suppressing the recombination of carriers in the semiconductor substrate, the content of metal such as iron, tungsten, gold, nickel, chromium, manganese, etc. In the composition for forming a barrier layer, the content is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 1% by mass or less.

The viscosity at 25 ° C. of the composition for forming a barrier layer is 1 Pa · s to 100 Pa · s.
In the present specification, the viscosity means a predetermined conversion factor to a measured value when an EMD type rotational viscometer is rotated at 25 ° C. for 1 minute at predetermined times (min ⁻¹ , 1/60 sec ⁻¹ ). It is defined as a value multiplied by. Conversion factor, different depending on the type of rotational speed and corn used. In the present specification, the viscosity of the composition for forming a barrier layer maintained at 25 ± 1 ° C. is measured using an EMD type rotational viscometer equipped with a cone rotor having a cone angle of 3 ° and a cone radius of 14 mm.

The composition for forming a barrier layer of the present invention has a viscosity of 1 Pa · s to 100 Pa · s measured at a rotation speed of 0.5 min ^{−1 to 5} min ⁻¹ with an EHD type rotational viscometer at 25 ° C. It is more preferably s to 80 Pa · s, further preferably 10 Pa · s to 80 Pa · s, and particularly preferably 10 Pa · s to 60 Pa · s. When the barrier layer-forming composition has a viscosity of 1 Pa · s or more, dripping hardly occurs when applied to a semiconductor substrate, and when it is 100 Pa · s or less, a fine coating pattern can be formed.

  The composition for forming a barrier layer of the present invention is a mixture of a specific silicon-containing compound, an organic binder, a dispersion medium, and components added as necessary using a blender, mortar, rotor, rotation / revolution mixer, and the like. You can get it. Moreover, when mixing, you may add a heat | fever as needed. The heating temperature at this time can be 30 degreeC-100 degreeC, for example.

<Semiconductor substrate with barrier layer>
The semiconductor substrate with a barrier layer of the present invention includes a semiconductor substrate and a barrier layer that is a dried body of the composition for forming a barrier layer provided on the semiconductor substrate. By providing the barrier layer over the semiconductor substrate, the impurity diffusion layer can be selectively formed in a region other than the region where the barrier layer is provided.

There are no particular limitations on the application amount of the semiconductor substrate a barrier layer forming ^composition, it is ^{preferably, 0.1g / m 2 ~20g / m} 2 to 0.01g / ^{m 2} ~100g / m 2 It is preferable. There is no restriction | limiting in particular in the thickness of the barrier layer formed by providing the composition for barrier layer formation, It is preferable that they are 0.1 micrometer-50 micrometers, and it is more preferable that they are 1 micrometer-30 micrometers.

  The barrier layer is a dried body of the barrier layer forming composition, and is formed by removing at least a part of the dispersion medium contained in the barrier layer forming composition. As a method for removing the dispersion medium, for example, a method of performing heat treatment at a temperature of about 80 ° C. to 500 ° C. for 1 minute to 10 minutes when using a hot plate, or 10 minutes to 30 minutes when using a dryer or the like. Can be mentioned. The heat treatment conditions are adjusted according to the type and content of the dispersion medium of the barrier layer forming composition, and are not particularly limited to the above conditions in the present invention.

  The content rate (residual rate) of the dispersion medium in the barrier layer is not particularly limited. The content of the dispersion medium in the barrier layer is preferably 30% by mass or less, more preferably 0.01% by mass to 15% by mass, and further preferably 0.1% by mass to 5% by mass. preferable. The content of the dispersion medium in the barrier layer can be calculated from the content of the nonvolatile component in the barrier layer forming composition and the amount of the barrier layer forming composition applied to the semiconductor substrate.

<Method for Manufacturing Solar Cell Substrate and Solar Cell Element>
In the method for producing a solar cell substrate of the present invention, the barrier layer forming composition is formed on a semiconductor substrate to form a patterned barrier layer, and the barrier layer on the semiconductor substrate is formed. And a step of diffusing a donor element or an acceptor element in a portion where the diffusion layer is not formed to partially form a diffusion layer in the semiconductor substrate.
Moreover, the manufacturing method of the solar cell element of this invention includes the process of forming an electrode on the diffusion layer of the board | substrate for solar cells obtained by the said manufacturing method.

  Here, the manufacturing method of the board | substrate for solar cells and the solar cell element using the composition for barrier layer formation of this invention is demonstrated, referring FIG. FIG. 1 is a schematic cross-sectional view conceptually showing an example of a manufacturing process of a solar cell substrate and a solar cell element of the present invention.

In addition, although FIG. 1 demonstrates the board | substrate for solar cell and a solar cell element of a back electrode type, the composition for barrier layer formation of this invention is applicable to the board | substrate for solar cells and a solar cell element of any type.
Examples of other types other than the back electrode type include a selective emitter type and a double-sided light receiving type. In the selective emitter type solar cell substrate, a diffusion layer having a dopant concentration higher than that of other regions is formed immediately below the electrode on the light receiving surface side. The barrier layer forming composition of the present invention can be used to form the high concentration diffusion layer region. Also, in a double-sided light receiving solar cell element, finger bars and bus bars are formed on both surfaces as electrodes, an n ⁺ type diffusion layer is formed on one surface of the semiconductor substrate, and a p ⁺ type diffusion layer is formed on the other surface. ing. In order to selectively form the n ⁺ -type diffusion layer and the p ⁺ -type diffusion layer, the barrier layer forming composition of the present invention can be used.

In FIG. 1A, an alkaline solution is applied to a silicon substrate which is an n-type semiconductor substrate 10 to remove a damaged layer, and a texture structure is obtained by etching.
Specifically, the damaged layer on the surface of the silicon substrate generated when slicing from the ingot is removed with a 20% by mass aqueous sodium hydroxide solution. Next, the silicon substrate is etched with an aqueous solution containing a 1 mass% sodium hydroxide aqueous solution and 10 mass% isopropyl alcohol to form a texture structure on the n-type semiconductor substrate 10 (the description of the texture structure is omitted in the figure). In the solar cell element, by forming a texture structure on the light receiving surface side of the n-type semiconductor substrate 10, a light confinement effect is promoted and high efficiency is achieved.

  In FIG. 1 (2), the barrier layer forming composition of the present invention is applied to the light receiving surface of the n-type semiconductor substrate 10 and the back surface opposite to the light receiving surface to form the barrier layer 11. In the present invention, the application method is not limited, and examples thereof include a printing method, a spin coating method, a brush coating method, a spray method, a doctor blade method, a roll coating method, and an ink jet method, and it is preferable to use a screen printing method.

There is no particular limitation as application amount of the composition for forming a barrier layer, it is possible to 0.01 g / ^{m 2} or more 100 g / ^{m 2} or less and preferably, 0.1 g / ^{m 2} or more 20 g / ^{m 2} or less Is more preferable. There is no restriction | limiting in particular in the application | coating thickness of the said composition for barrier layer formation, It is preferable that they are 0.1 micrometer or more and 50 micrometers or less, and it is more preferable that they are 1 micrometer or more and 30 micrometers or less.

  Depending on the composition of the barrier layer forming composition, a drying step for volatilizing the dispersion medium contained in the composition may be necessary after application. In this case, drying is performed at a temperature of about 80 ° C. to 300 ° C. for 1 minute to 10 minutes when a hot plate is used, and about 10 minutes to 30 minutes when a dryer or the like is used. The drying conditions are adjusted according to the content of the dispersion medium of the barrier layer forming composition, and are not particularly limited to the above conditions in the present invention. In this case, the barrier layer can be obtained as a dried product obtained by drying the barrier layer forming composition.

  On the back surface, a barrier layer is formed in a pattern. In the case of a printing method, an inkjet method or the like, the patterned barrier layer is obtained by applying the barrier layer forming composition 11 in a pattern shape. On the other hand, in the case of spin coating method, brush coating, spraying method, doctor blade method, roll coating method, etc., after the barrier layer forming composition 11 is applied to the entire surface, it is partially removed by etching or the like. A barrier layer is obtained.

Next, in FIG. 1C, coating diffusion materials 12 and 13 for forming an n ⁺ type diffusion layer and a p ⁺ type diffusion layer are applied. Next, in FIG. 1 (4), an n ⁺ -type diffusion layer 14 and a p ⁺ -type diffusion layer 15 are formed on the n-type semiconductor substrate 10 by thermal diffusion. By the heat treatment for thermal diffusion, the coating diffusion materials 12 and 13 become heat-treated products (baked products) 12 ′ and 13 ′ of the coating diffusion material, and generally form a glass layer. Although there is no restriction | limiting in particular as the heat processing temperature for thermal diffusion, It is preferable to heat-process on the conditions for 1 minute-300 minutes at the temperature of 750 to 1050 degreeC.

Here, a method of forming the n ⁺ -type diffusion layer 14 and the p ⁺ -type diffusion layer 15 in a lump is shown, but they may be diffused individually. For example, first, the coating diffusion material 13 for forming the p ⁺ -type diffusion layer 15 is applied and thermally diffused to remove the heat-treated product (baked product) 13 ′ of the coating diffusion material, and then the n ⁺ -type diffusion layer 14. The diffusion material for application 12 for forming the film may be applied and thermally diffused, and the heat-treated product (baked product) 12 ′ of the diffusion material for application may be removed.

Although the case where the coating diffusion materials 12 and 13 are used has been described here, the present invention can be similarly applied to a method using POCl ₃ gas or BBr ₃ gas. In that case, first, in the n-type semiconductor substrate 10, a region where the p ⁺ -type diffusion layer 15 is to be formed is used as an opening, and the barrier layer 11 is formed using a barrier layer forming composition other than the region used as the opening. Then, after forming the p ⁺ -type diffusion layer 15 in the n-type semiconductor substrate 10 corresponding to the opening, the barrier layer 11 is removed. Next, a region in which the n ⁺ -type diffusion layer 14 is to be formed is an opening, and the barrier layer 11 is formed using the barrier layer forming composition other than the region to be the opening. Then, an n ⁺ type diffusion layer 14 is formed in the n type semiconductor substrate 10 corresponding to the opening.

Next, in FIG. 1 (5), the barrier layer 11 and the heat-treated products (fired products) 12 ′ and 13 ′ of the diffusion material for coating are removed to obtain a solar cell substrate. Examples of the removal method include a method of immersing in an aqueous solution containing an acid, and a heat-treated product of a coating diffusion material for forming the barrier layer 11, the n ⁺ -type diffusion layer 14 and the p ⁺ -type diffusion layer 15. (Baking product) It is preferable to determine by the composition of 12 'and 13'. Specifically, the method includes a step of etching the glass layers [heat treated products (baked products) 12 ′ and 13 ′] and the barrier layer 11 formed on the semiconductor substrate by a thermal diffusion treatment with an aqueous solution containing hydrofluoric acid. preferable.

  Next, in FIG. 1 (6), an antireflection layer 16 is provided on the light receiving surface, and a passivation layer 17 is provided on the back surface. The antireflection layer 16 and the passivation layer 17 may have the same composition or different compositions. Examples of the antireflection layer 16 include a silicon nitride layer, and examples of the passivation layer 17 include a silicon oxide layer. There is no restriction | limiting in particular in the thickness of an antireflection layer and a passivation layer, It is preferable to set it as 10 nm-300 nm, and it is more preferable to set it as 30 nm-150 nm.

Next, in FIG. 1 (7), portions where electrodes are formed are opened in the passivation layer 17 on the n ⁺ -type diffusion layer 14 and the p ⁺ -type diffusion layer 15 (on the back surface side). There is no particular limitation on the method of opening, and for example, an opening can be formed by applying an etching solution (for example, a solution containing hydrofluoric acid, ammonium fluoride, or phosphoric acid) to a portion where the opening is desired by an inkjet method or the like, and performing heat treatment. .

Next, in FIG. 1 (8), an n electrode 18 and a p electrode 19 are formed on the n ⁺ -type diffusion layer 14 and the p ⁺ -type diffusion layer 15 (on the back surface side), respectively. In the present invention, the material and forming method of the n electrode 18 and the p electrode 19 are not particularly limited. For example, the n-electrode 18 and the p-electrode 19 may be formed by applying an electrode forming paste containing aluminum, silver, or copper and drying the paste. Next, the n-electrode 18 and the p-electrode 19 are heat-treated (fired) to complete the solar cell element.

  If the electrode forming paste contains glass frit, the step of opening shown in FIG. 1 (7) can be omitted. When an electrode forming paste containing glass frit is applied on the passivation layer 17 and heat-treated (baked) for several seconds to several minutes in the range of 600 ° C. to 900 ° C., the glass frit melts the passivation layer 17 on the back surface side, and paste The metal particles (for example, silver particles) inside form a contact portion with the silicon substrate 10 and solidify. Thereby, the formed back surface electrodes 18 and 19 and the silicon substrate 10 are electrically connected. This is called fire-through.

<Solar cell>
The solar cell includes at least one of the solar cell elements, and is configured by arranging a wiring material on the electrode of the solar cell element. In the solar cell, a plurality of solar cell elements may be connected via a wiring material as necessary, and may be further sealed with a sealing material.
The wiring material and the sealing material are not particularly limited, and can be appropriately selected from those usually used in the industry.

  Examples of the present invention will be described more specifically below, but the present invention is not limited to these examples. Unless otherwise stated, all chemicals used were reagents. “%” Means “% by mass” unless otherwise specified.

<Example 1>
(Preparation of barrier layer forming composition 11)
Add 1.5 g of ethylcellulose (Dow Chemical “Etocel STD200”, (Etocel) is a registered trademark) to 8.5 g of Terpineol (Nippon Terpene Chemical Co., Ltd. “Terpineol-LW”), dissolve at 150 ° C. for 1 hour, and 15 A mass% ethylcellulose / terpineol solution was prepared.
Ethyl silicate (Tama Chemical Co., Ltd. “Silicate 40”, SiO ₂ equivalent: 40%) 1.5 g (silicon compound is 6% by mass in terms of SiO ₂ ), 15% ethyl cellulose / terpineol solution 4.3 g (ethyl cellulose: 6.45% by mass) and 4.2 g of terpineol (terpineol: 63.55% by mass) were put in a plastic container. This was mixed for 10 minutes using a rotation / revolution mixer (Sinky Corporation “AR-100”) to prepare a composition 11 for forming a barrier layer.

This barrier layer-forming composition 11 had a viscosity of 25 Pa · s at 25 ° C. and 5 min ⁻¹ . The viscosity was measured using an EHD type viscometer (Tokyo Keiki Co., Ltd., cone angle: 3 °, cone radius: 14 mm), and the sampling amount of the barrier layer forming composition was 0.4 ml.

(Preparation of phosphorus diffusion solution)
A 20% by mass aqueous solution of ammonium dihydrogen phosphate (Wako Pure Chemical Industries, Ltd.) was prepared, and the supernatant saturated aqueous ammonium dihydrogen phosphate solution was used as the phosphorus diffusion solution.

(Thermal diffusion and etching process)
On the surface of the textured n-type silicon substrate (hereinafter also referred to as “n-type silicon substrate”), the barrier layer forming composition 11 was applied by screen printing (MT-320T, Micro Tech Co., Ltd.), and 150 ° C. After drying for 5 minutes on a hot plate, the substrate was dried for 1 minute on a hot plate at 500 ° C. This is a substrate with a barrier layer.
Next, another silicon substrate was prepared, spin-coated with a phosphorus diffusion solution at 500 min ⁻¹ (Mikasa Corporation, MS-A100), and dried at 200 ° C. This is a counter diffusion substrate.

  In a state where the substrate with the barrier layer and the counter diffusion substrate face each other at a distance of 1 mm, the substrate was heated at 850 ° C. for 30 minutes to diffuse phosphorus into the substrate with the barrier layer. Thereafter, the substrate with the barrier layer was immersed in a 10% by mass hydrochloric acid aqueous solution for 5 minutes, washed with water, and further immersed in a 2.5% by mass hydrofluoric acid aqueous solution for 5 minutes. This was washed with water and dried, and then evaluated as follows.

(Sheet resistance measurement)
The sheet resistance of the substrate to which the barrier layer-forming composition was applied was measured by a four-probe method using a Mitsubishi Chemical Corporation, Loresta-EP MCP-T360 type low resistivity meter. The sheet resistance of the portion where the barrier layer forming composition 11 was applied was 190Ω / □. The sheet resistance of the uncoated part was 40Ω / □.

  As a reference sample, the n-type silicon substrate after slicing was immersed in a 2.5 mass% HF aqueous solution for 5 minutes, washed with water, and measured for sheet resistance after drying. As a result, it was 240Ω / □. .

<Examples 2 to 6, Comparative Example 1>
A barrier layer forming composition having the composition shown in Tables 1 and 2 was prepared and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. The materials shown in Tables 1 and 2 are as follows. In the table, “-” indicates that no addition was made.
Methyl silicate: Tama Chemical Co., Ltd., product name “M silicate 51, SiO ₂ equivalent: 51% by mass
Polysilazane: AZ Electronic Materials, product name “NN110” (10 mass% polysilazane / xylene solution), SiO ₂ equivalent: about 13.3 mass%
Butyl carbitol acetate: Wako Pure Chemical Industries, Ltd. Silicon oxide: High Purity Chemical Laboratory, product name Silicon oxide (average particle size: 1 μm)

  As mentioned above, the semiconductor substrate of a dopant is contained by using the composition for barrier layer formation containing a specific silicon-containing compound, an organic binder, and a dispersion medium and having a viscosity at 25 ° C. of 1 Pa · s to 100 Pa · s. It has been found that the diffusion to can be sufficiently prevented. It was also found that surface roughness of the semiconductor substrate can be suppressed.

Claims (13)

A silicon-containing compound containing port Rishirazan contains an organic binder, and a dispersion medium, a viscosity at 25 ° C. is 1Pa · s~100Pa · s, a barrier layer forming composition. The composition for forming a barrier layer according to claim 1, wherein the content of the silicon-containing compound is 1% by mass to 18% by mass in terms of SiO ₂ . The composition for forming a barrier layer according to claim 1, wherein the content of the silicon-containing compound is 5% by mass to 16% by mass in terms of SiO ₂ . The composition for forming a barrier layer according to claim 1, wherein the content of the silicon-containing compound is 6% by mass to 13% by mass in terms of SiO ₂ .   The barrier layer-forming composition according to any one of claims 1 to 4, wherein the organic binder contains at least one selected from the group consisting of cellulose derivatives, acrylic resins, and alkyd resins.   The composition for barrier layer formation according to any one of claims 1 to 5, wherein the organic binder contains ethyl cellulose.   The barrier layer formation according to any one of claims 1 to 6, wherein the dispersion medium contains at least one selected from the group consisting of water, an alcohol solvent, an ether solvent, a glycol monoether solvent, and a terpene solvent. Composition.   The barrier layer forming composition according to any one of claims 1 to 6, wherein the dispersion medium contains at least one selected from the group consisting of terpineol, butyl carbitol, and butyl carbitol acetate.   The composition for barrier layer formation according to any one of claims 1 to 8, wherein a viscosity at 25 ° C is 10 Pa · s to 80 Pa · s. A semiconductor substrate;
A barrier layer that is a dried body of the composition for forming a barrier layer according to any one of claims 1 to 9, which is applied on the semiconductor substrate;
A semiconductor substrate with a barrier layer. Applying the barrier layer forming composition according to any one of claims 1 to 9 on a semiconductor substrate to form a patterned barrier layer;
A step of diffusing a donor element or an acceptor element in a portion where the barrier layer is not formed on the semiconductor substrate, and forming a diffusion layer partially in the semiconductor substrate;
The manufacturing method of the board | substrate for solar cells containing.   The method for producing a solar cell substrate according to claim 11, wherein the method for applying the barrier layer forming composition to the semiconductor substrate is a screen printing method.   The manufacturing method of a solar cell element including the process of forming an electrode on the diffusion layer of the board | substrate for solar cells obtained by the manufacturing method of Claim 11 or Claim 12.