JP2017045887A - n-TYPE DIFFUSION LAYER COMPOSITION, SEMICONDUCTOR SUBSTRATE AND MANUFACTURING METHOD THEREFOR, AND SOLAR CELL ELEMENT AND MANUFACTURING METHOD THEREFOR - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an n-type diffusion layer formation composition capable of diffusing n-type impurities uniformly to a desired part of a semiconductor substrate, and to provide a semiconductor substrate having an n-type diffusion layer formed by using the same and a manufacturing method therefor, and a solar cell element having the semiconductor substrate and a manufacturing method therefor.SOLUTION: An n-type diffusion layer formation composition contains glass particles containing a donor element, a dispersion medium, and a silicone compound.SELECTED DRAWING: None

Description

  The present invention relates to an n-type diffusion layer forming composition, a semiconductor substrate and a manufacturing method thereof, and a solar cell element and a manufacturing method thereof.

Currently, a large number of solar cells that are mass-produced include double-sided electrode type solar cells in which an n-type electrode is formed on the light receiving surface of a semiconductor substrate and a p-type electrode is formed on the back surface. However, in a double-sided electrode type solar cell, no sunlight is incident on a region immediately below the n-type electrode formed on the light-receiving surface, so that no current is generated in that portion. Therefore, a back electrode type solar cell has been proposed in which no electrode is formed on the light receiving surface of the solar cell, and both an n ⁺⁺ type electrode and a p ⁺ type electrode are formed on the back surface opposite to the light receiving surface. In this back electrode type solar cell, since the incidence of sunlight is not hindered by the electrode formed on the light receiving surface, high conversion efficiency can be expected in principle.

As a manufacturing method of a back electrode type solar cell, for example, the following manufacturing method is described in Patent Document 1.
First, a diffusion control mask is formed on the entire light receiving surface and back surface of a silicon substrate as a semiconductor substrate. Here, the diffusion control mask has a function of suppressing the diffusion of impurities into the silicon substrate. Next, a part of the diffusion control mask formed on the back surface of the silicon substrate is removed to form an opening. Then, n-type impurities such as phosphorus are diffused from the opening of the diffusion control mask to the back surface of the silicon substrate, and an n-type impurity diffusion layer is formed only in the opening. Next, after all of the diffusion control mask on the back surface of the silicon substrate is removed, an oxide film such as a silicon oxide film is formed on the entire back surface. Here, since the formation rate of the oxide film is different between the region where the n-type impurity diffusion layer is formed and the region where the n-type impurity diffusion layer is not formed, oxidation of the region where the n-type impurity diffusion layer is formed is performed. The physical film is formed thicker than the oxide film in the region where the n-type impurity diffusion layer is not formed.

  The reason why the oxide film in the region where the n-type impurity diffusion layer is formed is thicker than the oxide film in the region where the n-type impurity diffusion layer is not formed is as follows. In the region where the n-type impurity diffusion layer is not formed, silicon atoms are firmly bonded by Si—Si covalent bonds. When this region is oxidized, oxygen atoms break a covalent bond between silicon atoms and intervene between Si-Si, and oxidation proceeds by forming a Si-O-Si bond. The Si-Si supply bond has high bond energy, and high temperature and long time heating are required for oxidation. On the other hand, in the region where the n-type impurity diffusion layer is formed, a large amount of phosphorus, which is a donor atom, is diffused, and most of the silicon atoms in the silicon substrate are replaced with phosphorus atoms. In the region where the n-type impurity diffusion layer is formed, generally, 10 19 to 21 21 phosphorus atoms are diffused per cubic centimeter, and many of them are replaced with silicon atoms. A bond between a phosphorus atom and a silicon atom (P—Si bond) has strong ionic bond properties and a bond energy smaller than that of a Si—Si covalent bond. Therefore, during the oxidation treatment, the P—Si bond is more easily broken by oxygen atoms than the Si—Si bond. Therefore, the region in which the n-type impurity diffusion layer is formed has a higher oxidation rate than the region in which the n-type impurity diffusion layer is formed, and as a result, a thick oxide film is formed.

  Subsequently, the oxide film other than the region where the n-type impurity diffusion layer is formed is completely removed by etching. Although the thickness of the oxide film in the region where the n-type impurity diffusion layer is formed is also reduced by etching, it is not completely removed because it is thicker than the oxide film in the region where the n-type impurity diffusion layer is not formed. Part remains. The remaining oxide film functions as a barrier film in the subsequent p-type impurity diffusion treatment. Subsequently, a p-type impurity diffusion layer is formed in a region other than the region where the n-type impurity diffusion layer is formed where the oxide film as the barrier film remains. Furthermore, a back electrode type solar cell is completed by forming a texture structure, an antireflection film, a passivation film, an electrode, and the like.

JP 2014-86587 A

  In the above method, the oxide film on the n-type impurity diffusion layer region must be formed thick so as not to be completely removed by the etching process. If this oxide film is thin, it will not function as a barrier film during subsequent p-type impurity diffusion treatment, and p-type impurities such as boron will diffuse into the region where the n-type impurity diffusion layer is formed, resulting in semiconductor characteristics. May deteriorate. In addition, it is desirable that the oxide film remaining as the barrier film has a uniform thickness. If there is an insufficiently thick region in part of the oxide film, p-type impurities such as boron diffuse from there, and the semiconductor characteristics may be deteriorated.

  In order to form an oxide film having a sufficiently uniform thickness in the n-type impurity diffusion layer region, the amount of n-type impurity applied is increased or the n-type impurity concentration in the n-type impurity forming composition is increased. It is necessary to increase the diffusion amount of n-type impurities. However, from the viewpoint of manufacturing cost or productivity at the time of mass production of solar cell elements, it is desired to reduce the amount of the n-type diffusion layer forming composition used for production of one solar cell element. For example, 1 mg or less per square centimeter is desired. When the conventional n-type diffusion layer forming composition has the above coating amount, the diffusion of n-type impurities is insufficient in the microscopic region, and the thickness of the oxide film formed there is insufficient. Therefore, an n-type diffusion layer forming composition that enables sufficiently uniform diffusion of n-type impurities with a limited coating amount is desired.

  The present invention has been made in view of the above circumstances, and has an n-type diffusion layer forming composition capable of uniformly diffusing n-type impurities in a desired portion of a semiconductor substrate, and an n-type diffusion layer formed using the same. It is an object of the present invention to provide a semiconductor substrate and a manufacturing method thereof, a solar cell element having the semiconductor substrate, and a manufacturing method thereof.

Means for solving the above problems include the following embodiments.
<1> An n-type diffusion layer forming composition containing glass particles containing a donor element, a dispersion medium, and a silicone compound.
<2> The n-type diffusion layer forming composition according to <1>, wherein the donor element is at least one selected from the group consisting of P (phosphorus) and Sb (antimony).
<3> At least one donor element-containing material selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O _3, wherein the glass particles containing the donor element are SiO ₂ , K ₂ O, At least one glass component material selected from the group consisting of Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ and MoO ₃ And the n type diffused layer formation composition as described in <1> or <2> containing.
<4> The n-type diffusion layer forming composition according to any one of <1> to <3>, wherein the silicone compound has a weight average molecular weight of 1,000 to 100,000.
<5> A semiconductor substrate having an n-type diffusion layer formed using the n-type diffusion layer forming composition according to any one of <1> to <4>.
<6> The n-type diffusion layer forming composition according to any one of <1> to <4> is applied to at least a part of at least one surface of the semiconductor substrate to form an n-type diffusion layer forming composition layer. The manufacturing method of a semiconductor substrate including the process of forming, and the process of heat-processing the said n type diffused layer formation composition layer and forming an n type diffused layer.
<7> A semiconductor substrate having an n-type diffusion layer formed using the n-type diffusion layer forming composition according to any one of <1> to <4>, and an electrode provided on the semiconductor substrate; And a solar cell element.
<8> A solar cell including a step of providing an electrode on a semiconductor substrate having an n-type diffusion layer formed using the n-type diffusion layer forming composition according to any one of <1> to <4>. Device manufacturing method.

  According to the present invention, an n-type diffusion layer forming composition capable of uniformly diffusing n-type impurities in a desired portion of a semiconductor substrate, a semiconductor substrate having an n-type diffusion layer formed using the same, a method for manufacturing the same, and A solar cell element having the semiconductor substrate and a manufacturing method thereof are provided.

It is sectional drawing which shows notionally an example of the manufacturing method of the semiconductor substrate of the embodiment of this invention, and a solar cell element.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless explicitly specified, unless otherwise clearly considered essential in principle. The same applies to numerical values and ranges thereof, and the present invention is not limited thereto.

  In this specification, the term “process” is not limited to an independent process, and is included in this term if the purpose of the process is achieved even when it cannot be clearly distinguished from other processes. In the present specification, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. In addition, in the present specification, the content of each component in the composition is such that when there are a plurality of substances corresponding to each component in the composition, the plurality of substances present in the composition unless otherwise specified. Means the total amount. In the present specification, the particle diameter of each component in the composition is such that when there are a plurality of particles corresponding to each component in the composition, the plurality of particles present in the composition unless otherwise specified. The value for a mixture of

  In this specification, “content ratio” represents mass% of each component when the total amount of the n-type diffusion layer forming composition is 100 mass% unless otherwise specified. In addition, in this specification, the term “layer” or “film” includes a configuration formed in a part in addition to a configuration formed over the entire surface when observed as a plan view. Is included.

  Hereinafter, first, the n-type diffusion layer forming composition used in the present invention will be described. Next, the manufacturing method of the semiconductor substrate using these n type diffused layer formation compositions and the manufacturing method of a solar cell element are demonstrated.

<N-type diffusion layer forming composition>
The n-type diffusion layer forming composition of an embodiment of the present invention contains glass particles containing a donor element, a dispersion medium, and a silicone compound. The n-type diffusion layer forming composition may contain other components as necessary in consideration of the imparting property, the removability after forming the n-type diffusion layer, and the like.

  Here, the n-type diffusion layer forming composition contains a donor element which is an n-type impurity, and after applying to the semiconductor substrate, the donor element is thermally diffused, thereby forming the n-type diffusion layer forming composition of the semiconductor substrate. The material which can form an n-type diffused layer in the site | part which provided. By using the n-type diffusion layer forming composition, an n-type diffusion layer can be selectively formed only in a desired portion without forming an unnecessary n-type diffusion layer on the back surface, side surface, or the like of the semiconductor substrate.

Therefore, when the n-type diffusion layer forming composition is applied, the side etching step performed by the conventionally widely used gas phase reaction method becomes unnecessary, and the process tends to be simplified. Further, there is no need to convert the n-type diffusion layer formed on the back surface of the semiconductor substrate into a p ⁺ -type diffusion layer. Therefore, options such as the method for forming the p ⁺ -type diffusion layer on the back surface, the material, shape, and thickness of the back surface electrode are expanded. Moreover, although mentioned later for details, generation | occurrence | production of the internal stress in the semiconductor substrate resulting from the thickness of a back surface electrode is suppressed, and it exists in the tendency for the curvature of a semiconductor substrate to be suppressed.

  The glass particles contained in the n-type diffusion layer forming composition are melted by heat treatment to form a glass layer on the n-type diffusion layer. However, a glass layer is formed on the n-type diffusion layer even in a conventional gas phase reaction method, a method of applying a phosphate-containing solution, or the like. Therefore, the glass layer produced | generated in this invention can be removed by an etching similarly to the conventional method. Therefore, the n-type diffusion layer forming composition does not generate unnecessary products and does not increase the number of steps as compared with the conventional method.

  In addition, since the donor element in the glass particles does not volatilize outside even during the heat treatment, the n-type diffusion layer tends to be prevented from being formed on the back surface or side surface of the semiconductor substrate due to the generation of the volatilizing gas. The reason for this is considered to be that, for example, the donor component is bonded to an element derived from the glass component substance in the glass particles or is taken into the glass, so that it is difficult to volatilize.

(Glass particles)
The glass particles containing the donor element according to the present invention will be described in detail.
The donor element means an element that can form an n-type diffusion layer by doping into a semiconductor substrate. As the donor element, an element belonging to Group 15 can be used, and examples thereof include P (phosphorus), Sb (antimony), and As (arsenic). From the viewpoint of safety, easiness of vitrification, etc., the donor element preferably contains at least one selected from the group consisting of P (phosphorus) and Sb (antimony).
In the present specification, the glass particles mean particles in which glass (an amorphous solid exhibiting a glass transition phenomenon) is formed into particles.

As the donor element-containing substance used to introduce the donor element to the glass _{particles, P 2 O 3, P 2} O 5, Sb 2 O 3, Bi 2 O 3, As 2 O 3 and the _{like, P} 2 O ₃ , at least one selected from the group consisting of P ₂ O ₅ and Sb ₂ O ₃ is preferably used.

  The glass particles containing a donor element can control the melting temperature, softening point, glass transition point, chemical durability, and the like by adjusting the component ratio as necessary. From this viewpoint, it is preferable that the glass particle containing a donor element further contains the components described below.

Examples of glass component materials include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ , WO ₃ , MoO ₃ , MnO, Examples include La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , ZrO ₂ , GeO ₂ , TeO ₂ , and Lu ₂ O ₃ . Glass particles containing a donor element are SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ , WO ₃ , MoO ₃ and It is preferable that at least one selected from the group consisting of MnO is included as a glass component substance. Glass particles containing a donor element are SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ and MoO. More preferably, at least one selected from the group consisting of ₃ is included as a glass component substance.

Glass particles containing a donor element include at least one donor element-containing material selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ , SiO ₂ , K ₂ O, Na ₂ O, Containing at least one glass component material selected from the group consisting of Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ and MoO ₃ It is preferable to do.
In the present specification, the glass particle containing a donor element “includes” a donor element-containing substance means that it contains a component of the donor element-containing substance, and “includes” a glass component substance means the glass component substance It means that it contains the component of.

Specific examples of the glass particles containing a donor element include P ₂ O ₅ —SiO ₂ glass particles, P ₂ O ₅ —K ₂ O glass particles, P ₂ O ₅ —Na ₂ O glass particles, and P ₂ O. ₅ -Li ₂ O system glass _particles, P ₂ O 5 -BaO-based glass _particles, P ₂ O 5 -SrO based glass _particles, P ₂ O 5 -CaO-based glass _particles, P ₂ O 5 -MgO-based glass particles, P ₂ O ₅ -BeO glass _particles, P ₂ O 5 -ZnO-based glass _particles, P ₂ O 5 -CdO glass _particles, P ₂ O 5 -PbO based glass _particles, P ₂ O 5 -SnO-based glass particles, P ₂ O ₅ -GeO ₂ glass _{particles, P 2 O 5 -Sb 2 O} 3 based glass _particles, P ₂ O 5 -TeO ₂ glass _{particles, P 2 O 5 -As 2 O} 3 system _{P 2} of the glass particles and the like O ₅ based glass particles, _Sb 2 _{O 3} Glass particles, and the like.

In the above it has been illustrated composite glass containing two _{components, P 2 O 5 -SiO 2 -CaO} , or may be a composite glass particles containing 3 or more components, such as P ₂ O ₅ -SiO ₂ -MgO.

  The content of the glass component substance in the glass particles containing the donor element is preferably set as appropriate in consideration of the melting temperature, softening point, glass transition point, chemical durability, and the like. The content of the glass component substance is preferably 0.1% by mass to 95% by mass, and more preferably 0.5% by mass to 90% by mass.

  The softening point of the glass particles containing the donor element is preferably 200 ° C. to 1000 ° C. from the viewpoint of diffusibility of components of the n-type diffusion layer forming composition during heat treatment, suppression of dripping, etc. More preferably, it is 900 ° C.

  Examples of the shape of the glass particles containing the donor element include a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and a needle shape. The glass particles are preferably substantially spherical, flat or plate-like from the viewpoint of application properties to a semiconductor substrate, uniform diffusibility, and the like when an n-type diffusion layer forming composition is used.

The average particle diameter of the glass particles containing the donor element is preferably 100 μm or less. When glass particles having an average particle diameter of 100 μm or less are used, a smooth composition layer is easily obtained. Furthermore, the average particle diameter of the glass particles is preferably 50 μm or less, and more preferably 30 μm or less. The lower limit is not particularly limited, but is preferably 0.01 μm or more.
In this specification, the average particle diameter of the glass particle containing a donor element represents a volume average particle diameter, and can be measured with a laser scattering diffraction particle size distribution analyzer or the like. Specifically, it means the particle diameter corresponding to 50% of the cumulative volume from the small diameter side in the particle size distribution.

The glass particle containing a donor element can be produced, for example, by the following procedure.
First, a donor element-containing material and a glass component material, which are raw materials for glass particles containing a donor element, are heated and melted in an electric furnace or the like. The melt is then vitrified. The obtained glass is pulverized into particles of a desired size. The pulverization can be performed by a known method.

  The content of the glass particles containing the donor element in the n-type diffusion layer forming composition is determined in consideration of the imparting property, the diffusibility of the donor element, and the like. In general, the content of the glass particles in the n-type diffusion layer forming composition is preferably 0.1% by mass to 95% by mass with respect to the total mass of the n-type diffusion layer forming composition. % To 90% by mass is more preferable, and 2% to 80% by mass is even more preferable.

It is preferable that the content rate of the glass particle containing the donor element in an n type diffused layer formation composition is 0.1 mass%-99 mass% with respect to the total amount of the non-volatile component of an n type diffused layer formation composition. The content is more preferably 1% by mass to 95% by mass, and further preferably 2% by mass to 90% by mass.
Here, the “nonvolatile component” means a component in the n-type diffusion layer forming composition other than a volatile substance such as a solvent described later. Here, the volatile substance means a substance having a boiling point of 250 ° C. or lower under atmospheric pressure.

(Dispersion medium)
Next, the dispersion medium will be described. The dispersion medium is a medium in which the glass particles are dispersed in the n-type diffusion layer forming composition. As the dispersion medium, a binder, a solvent, or the like is used.

  Examples of the binder include dimethylaminoethyl (meth) acrylate polymer, polyvinyl alcohol, polyacrylamides, polyvinylamides, polyvinylpyrrolidone, poly (meth) acrylic acids, polyethylene oxides, polysulfonic acid, acrylamide alkyl sulfonic acid, and cellulose ether. , Cellulose derivatives, carboxymethyl cellulose, hydroxyethyl cellulose, ethyl cellulose, gelatin, starch and starch derivatives, sodium alginate, xanthan, guar gum and guar gum derivatives, scleroglucan, tragacanth, dextrin derivatives, acrylic acid resin, acrylic ester resin, butadiene Resins, styrene resins, copolymers of monomers that make up these resins, and silicon dioxide It is. A binder is used individually by 1 type or in combination of 2 or more types.

  The weight average molecular weight of the binder is not particularly limited, and it is desirable to adjust appropriately in consideration of a desired viscosity as the n-type diffusion layer forming 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, and dipropyl. Ketone solvents such as ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone, γ-butyrolactone, γ-valerolactone, diethyl ether, methyl ethyl ether, Methyl-n-di-n-propyl ether, diisopropyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethyl Glycol diether ether, ethylene glycol di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl mono-n-propyl ether, diethylene glycol methyl mono-n-butyl ether, diethylene glycol di -N-propyl ether, diethylene glycol di-n-butyl ether, diethylene glycol methyl mono-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl mono-n-butyl ether, Triecile Glycol di-n-butyl ether, triethylene glycol methyl mono-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl mono-n-butyl ether, diethylene glycol di-n -Butyl ether, tetraethylene glycol methyl mono-n-hexyl ether, tetraethylene glycol di-n-butyl ether, 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 mono-n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl mono-n-hexyl ether, tripropylene glycol Dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl ethyl ether, tripropylene glycol methyl mono-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl mono-n-hexyl ether, tetrapropylene glycol dimethyl ether, Tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl Ether solvents such as ether, tetrapropylene glycol methyl mono-n-butyl ether, dipropylene glycol di-n-butyl ether, tetrapropylene glycol methyl mono-n-hexyl ether, tetrapropylene glycol di-n-butyl ether, methyl acetate, acetic acid Ethyl, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, acetic acid 2 -Ethylhexyl, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, diethylene glycol monomethyl acetate Ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, glycol diacetate, methoxytriethylene glycol acetate, ethyl propionate, n-butyl propionate Ester solvents such as isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, Diethylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol Cole-n-butyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether acetate and other ether acetate solvents, acetonitrile, N-methyl Pyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylsulfoxide, methanol, Ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-but Tanol, t-butanol, n-pentanol, isopentanol, 2-methylbutanol, sec-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2 -Ethylbutanol, sec-heptanol, 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, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene Alcohols such as ethylene glycol, triethylene glycol, tripropylene glycol, terpineol, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, Ether solvents such as diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, Methyl lactate, ethyl lactate Lactate n- butyl, ester solvents such as lactic acid n- amyl and water. These solvents are used alone or in combination of two or more.

  The content of the dispersion medium in the n-type diffusion layer forming composition is determined in consideration of the coating property, the concentration of the donor element, and the like. The viscosity of the n-type diffusion layer forming composition is preferably 10 mPa · s to 1,000,000 mPa · s, more preferably 50 mPa · s to 500,000 mPa · s in consideration of applicability.

(Silicone compound)
Next, the silicone compound will be described. By including the silicone compound in the n-type diffusion layer forming composition, n-type impurities can be uniformly diffused in a desired portion of the semiconductor substrate. As a result, the thickness of the oxide film formed after removing the glass layer from the region where the n-type diffusion layer is formed becomes more uniform, and a good function as a barrier layer is obtained. The reason is not clear, but is presumed as follows.

  The glass particles containing the donor element are melted by heating during the heat treatment, and the glass particles start to bond to form a glass layer. Here, when the amount of the glass particles on the semiconductor substrate is small, the glass particles are not melted and integrated, and a microscopic thin film region (hole, dent, etc.) may be generated in the glass layer. However, when the n-type diffusion layer-forming composition contains a silicone compound, the silicone compound is present so as to fill in the space between the glass particles, thereby promoting melting and integration of the glass particles. As a result, it is considered that the donor element contained in the glass particles diffuses more uniformly into the semiconductor substrate. In addition, a silicone compound turns into a silicon oxide by heat processing, and forms a glass layer with the glass component of a glass particle.

  As described above, the n-type diffusion layer formed using the n-type diffusion layer-forming composition containing the silicone compound is more than the n-type diffusion layer formed using the n-type diffusion layer-forming composition containing no silicone compound. N-type impurities are uniformly diffused. For this reason, the thickness of the oxide film formed on the n-type diffusion layer by performing the oxidation treatment after the removal of the glass layer becomes more uniform. As a result, an oxide film having a sufficiently uniform thickness remains on the n-type diffusion layer even after etching, and a barrier layer that suppresses diffusion of p-type impurities into the n-type diffusion layer performed in the p-type diffusion layer forming step. As well as it works.

  From the viewpoint of sufficiently obtaining the above effect, it is preferable that the silicone compound remains without disappearing until heat treatment for forming the n-type diffusion layer is performed. That is, when heating is performed to remove the dispersion medium contained in the n-type diffusion layer forming composition, the solid or liquid state is maintained at the temperature at which the dispersion medium is removed (for example, 200 ° C. to 500 ° C.). What you can do is desirable.

  In this specification, the silicone compound means a compound (polysiloxane) having a siloxane bond (Si—O—Si) in the main skeleton. Since silicon is tetravalent, it has four covalent bonding sites with other atoms. Two of the covalent bonding sites are bonded to oxygen, and the remaining two covalent bonding sites are bonded to various substituents.

  The substituent bonded to the silicon atom of the silicone compound is not particularly limited, for example, an aliphatic hydrocarbon group such as a methyl group, an aromatic hydrocarbon group such as a phenyl group, an ether bond-containing group, a hydroxyl group amino group, an amide group, Examples include a sulfonyl group, a sulfide bond-containing group, and a thiol group. Of these, a methyl group and a phenyl group are preferable, and a phenyl group is more preferable.

  Specific examples of the silicone compound include polymethylsiloxane and polymethylphenylsiloxane, with polymethylphenylsiloxane being preferred. A silicone compound may be used individually by 1 type, or may use 2 or more types together.

  The content rate of the silicone compound in the n-type diffusion layer forming composition is not particularly limited. For example, the content is preferably 0.1% by mass to 3% by mass. The effect of this invention is fully acquired as the content rate of a silicone compound is less than 0.1 mass%. When the content is 3% by mass or less, the diffusion of the donor element in the glass particles into the semiconductor substrate is hardly inhibited by the silicone compound.

  The weight average molecular weight of the silicone compound is not particularly limited. For example, it is preferably 1000 to 100,000. If the weight average molecular weight of the silicone compound is 1000 or less, decomposition and scattering in the gas phase tend to be suppressed during the diffusion treatment. When the weight average molecular weight of the silicone compound is 100,000 or more, the viscosity of the n-type diffusion layer forming composition does not increase excessively and good handling properties tend to be maintained.

(Other additives)
If necessary, the n-type diffusion layer forming composition may contain other additives. Examples of other additives include metals.

  The n-type diffusion layer forming composition is applied on a semiconductor substrate and heat-treated at a high temperature to form a glass layer when forming the n-type diffusion layer. This glass layer can be removed by etching. However, it may be difficult to remove depending on the type of glass formed. In that case, there is a tendency that the glass layer is easily removed by adding a metal that easily crystallizes with the glass layer to the n-type diffusion layer forming composition.

  Examples of the metal that easily crystallizes with the glass layer include Al, Ag, Mn, Cu, Fe, Zn, and Si. When the n-type diffusion layer forming composition contains a metal, the metal is preferably at least one selected from the group consisting of Al, Ag, Si, Cu, Fe, Zn and Mn, and consists of Al, Ag, Si and Zn. At least one selected from the group is more preferable, and Ag is still more preferable.

  When the n-type diffusion layer forming composition contains a metal, it is desirable to adjust the content appropriately according to the type of glass, the type of metal, and the like. Since the n-type diffusion layer forming composition is distinguished from the electrode forming composition, it is preferable not to use a metal that is a conductive material as a main component (a component that occupies 10% by mass of the n-type diffusion layer forming composition). .

  When the n-type diffusion layer forming composition contains a metal, the metal content in the n-type diffusion layer forming composition is based on 100% by mass of the glass particles from the viewpoint of not reducing the bulk lifetime of the semiconductor substrate. It is preferably 10% by mass or less, more preferably 7% by mass or less, and further preferably 5% by mass or less. When the n-type diffusion layer forming composition contains a metal, the metal content is preferably 0.01% by mass or more with respect to 100% by mass of the glass particles from the viewpoint of the glass layer removal efficiency. It is more preferably 1% by mass or more, and further preferably 3% by mass or more.

<Semiconductor substrate>
A semiconductor substrate having an n-type diffusion layer according to an embodiment of the present invention has an n-type diffusion layer formed using the above-described n-type diffusion layer forming composition.

  The kind in particular of a semiconductor substrate is not restrict | limited, The semiconductor substrate which can be used as a board | substrate of a solar cell element is applicable. For example, silicon substrate, gallium phosphide substrate, gallium nitride substrate, diamond substrate, aluminum nitride substrate, indium nitride substrate, gallium arsenide substrate, germanium substrate, zinc selenide substrate, zinc telluride substrate, cadmium telluride substrate, cadmium sulfide Examples include substrates, indium phosphide substrates, silicon carbide, silicon germanium substrates, and copper indium selenium substrates. Examples of the silicon substrate include a crystalline silicon substrate. The semiconductor substrate may be an n-type semiconductor substrate or a p-type semiconductor substrate.

The n-type diffusion layer of the semiconductor substrate is formed by applying the above-described n-type diffusion layer forming composition to the semiconductor substrate. The semiconductor substrate is preferably subjected to pretreatment before applying the n-type diffusion layer forming composition. Examples of the pretreatment include the following steps.
An alkali solution is applied to the semiconductor substrate to remove the damaged layer, and a texture structure is obtained by etching. Specifically, the damaged layer on the surface of the semiconductor substrate generated when slicing from the ingot is removed with a 20% by mass aqueous sodium hydroxide solution. Next, etching is performed with a mixed solution of 1% by mass caustic soda and 10% by mass isopropyl alcohol to form a texture structure. In the solar cell element, by forming a texture structure on the light receiving surface side, a light confinement effect is promoted and high efficiency is achieved.

<Semiconductor substrate manufacturing method>
In the method of manufacturing a semiconductor substrate according to the embodiment of the present invention, the n-type diffusion layer forming composition layer is formed by applying the n-type diffusion layer forming composition described above to at least a part of at least one surface of the semiconductor substrate. And a step of heat-treating the n-type diffusion layer forming composition layer to form an n-type diffusion layer.

  Details and preferred embodiments of the n-type diffusion layer forming composition and the semiconductor substrate used in the method for producing a semiconductor substrate are the same as the details and preferred embodiments of the n-type diffusion layer forming composition and the semiconductor substrate described above.

[N-type diffusion layer forming composition layer forming step]
In the method for manufacturing a semiconductor substrate, an n-type diffusion layer-forming composition containing glass particles containing a donor element and a dispersion medium is applied to at least a part of the semiconductor substrate before the heat treatment step, and the n-type diffusion is performed. A step of forming a layer forming composition layer (hereinafter also referred to as “n-type diffusion layer forming composition layer forming step”) may be included.

  A method for forming the n-type diffusion layer forming composition layer is not particularly 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. The shape of the region to which the n-type diffusion layer forming composition is applied can be appropriately changed according to the region where the n-type diffusion layer is to be formed.

  After forming the n-type diffusion layer forming composition layer, if necessary, at least a part of the dispersion medium may be removed by drying the n-type diffusion layer forming composition layer. A drying temperature is not specifically limited, For example, the temperature of about 80 to 300 degreeC is mentioned. For example, when using a hot plate, it can be dried for about 1 minute to 10 minutes, and when using a dryer or the like, it can be dried for about 10 minutes to 30 minutes. The drying conditions can be selected according to the dispersion medium composition of the n-type diffusion layer forming composition, and are not particularly limited to the above conditions in the present invention.

[Heat treatment process]
In the heat treatment step, the n-type diffusion layer forming composition layer is heat-treated to form an n-type diffusion layer. The heat treatment is performed, for example, under conditions where the gas flow rate is 3 mm / second to 60 mm / second in linear velocity. By performing the heat treatment, the toner element diffuses into the semiconductor substrate, and an n-type diffusion layer is formed. Furthermore, a glass layer such as phosphate glass is formed on the surface of the n-type diffusion layer.

  When the gas flow rate in the heat treatment step is 3 mm / second or more in terms of linear velocity, a high concentration of donor element tends to be diffused in the n-type diffusion layer to be formed. When the gas flow rate is 60 mm / second or less in linear velocity, it becomes easy to maintain the heat treatment temperature constant, and there is a tendency that a stable quality n-type diffusion layer cannot be obtained.

From the viewpoint of diffusing a higher concentration of the donor element, the gas flow rate is preferably 4 mm / second or more, more preferably 5 mm / second or more, and more preferably 6 mm / second or more in terms of linear velocity. preferable.
From the viewpoint of maintaining the heat treatment temperature, the gas flow rate is preferably 50 mm / second or less, more preferably 40 mm / second or less, further preferably 30 mm / second or less, and 20 mm / second in terms of linear velocity. It is particularly preferred that it be less than a second.

The heat treatment temperature is not particularly limited, and examples thereof include 600 ° C. to 1200 ° C. From the viewpoint of obtaining temperature uniformity in the heating apparatus, it is preferably 700 ° C. to 1150 ° C., and is preferably 750 ° C. to 1100 ° C. More preferably.
The heat treatment time is not particularly limited, and examples thereof include 1 minute to 60 minutes. From the viewpoint of mass productivity in the production of a semiconductor substrate having an n-type diffusion layer and a solar cell element described later, it is preferably 2 minutes to 40 minutes, and more preferably 3 minutes to 25 minutes.

  The type of gas in the heat treatment step is not particularly limited. Examples of the usable single gas include nitrogen gas, oxygen gas, hydrogen gas, helium gas, neon gas, argon gas, krypton gas, xenon gas, radon gas, and halogen gas. As the compound gas that can be used, an organic gas such as methane or propane, or a gas obtained from phosphorus oxychloride, boron tribromide, boron trichloride, or the like that can be gasified by heating can be used. These gases can be used alone or in combination of two or more. The gas in the heat treatment step may contain air.

  The gas in the heat treatment step preferably contains oxygen gas from the viewpoint of uniformly forming the n-type diffusion layer in a desired region on the semiconductor substrate. The mixing ratio of oxygen gas is not particularly limited. For example, it can be 10 volume%-100 volume% of the whole gas, and it is preferable that it is 30 volume%-90 volume%.

  The heat treatment step can be performed using a known continuous diffusion furnace, batch diffusion furnace or the like.

[First etching process]
The semiconductor substrate manufacturing method may further include a step of removing the glass layer formed on the semiconductor substrate by etching after the heat treatment step (hereinafter also referred to as “first etching step”). For example, after the heat treatment step, the semiconductor substrate can be cooled to room temperature (for example, 20 ° C. to 40 ° C.) and then etched.

  As an etching method in the first etching step, a known method such as a method of immersing in an acid such as hydrofluoric acid or a method of immersing in an alkali such as caustic soda can be applied.

  The glass layer formed on the surface of the n-type diffusion layer by the heat treatment step is formed by melting the glass particles at the above heat treatment temperature and cooling it. At this time, when the cooling rate is low, the crystal component is mixed in the glass layer, and subsequent removal by etching may be difficult, resulting in a residue. Therefore, the cooling rate is preferably in the range of 5 ° C./second to 300 ° C./second. When the cooling rate is 300 ° C./second or less, only the surface of the glass layer is suppressed from being rapidly cooled, the decrease in the cooling rate inside the glass layer is suppressed, and the formation of microcrystals is likely to be suppressed. It is in. Further, considering the control of the cooling rate using currently distributed thermal diffusion furnaces and the process time, the cooling rate is more preferably 10 ° C./second to 50 ° C./second.

  After the first etching, the semiconductor substrate from which the glass layer has been removed may be washed and dried.

[Oxidation treatment process]
The method for manufacturing a semiconductor substrate may further include a step of oxidizing the semiconductor substrate having an n-type diffusion layer (hereinafter also referred to as “oxidation step”). By the oxidation treatment, an oxide film such as a silicon oxide film is formed over the semiconductor substrate. The formation rate of the oxide film is higher in the region where the n-type impurity diffusion layer is formed than in the region where the n-type impurity diffusion layer is not formed. Therefore, the oxide film tends to be formed thicker in the region where the n-type diffusion layer is formed than in other regions.

The method for the oxidation treatment is not particularly limited, and is preferably at least one selected from the group consisting of dry oxidation and wet oxidation.
Dry oxidation means an oxidation method by treating at a high temperature in an oxygen gas atmosphere. Dry oxidation conditions are not particularly limited, and for example, it is preferable to perform a treatment at 800 ° C. to 1100 ° C. for 10 minutes to 240 minutes. Wet oxidation means an oxidation method by processing at a high temperature using oxygen gas and deionized water vapor. The conditions for wet oxidation are not particularly limited, and for example, it is preferable to perform treatment at 800 ° C. to 1100 ° C. for 10 minutes to 240 minutes.

[Second etching process]
The method for manufacturing a semiconductor substrate may further include a step of removing the oxide film formed on the semiconductor substrate by etching after the oxidation treatment step (hereinafter also referred to as “second etching step”).

  The second etching step may be performed such that the oxide film other than the region where the n-type diffusion layer is formed is sufficiently removed, and the oxide film remains in the region where the n-type diffusion layer is formed. preferable. As described above, the oxide film tends to be formed thicker in the region where the n-type diffusion layer is formed. Therefore, the oxide film other than the region where the n-type diffusion layer is formed is sufficiently removed, and the etching is stopped in a state where the oxide film remains in the region where the n-type diffusion layer is formed. The oxide film can be left in the region where the diffusion layer is formed. In order to sufficiently leave the oxide film in the region where the n-type diffusion layer is formed, for example, the thickness of the oxide film formed in the region where the n-type diffusion layer is formed is The thickness of the oxide film formed in a region other than the formed region is preferably 3 times or more, more preferably about 5 to 6 times.

  As an etching method in the second etching step, a known method such as a method using hydrofluoric acid, hydrofluoric acid, or the like can be applied.

[P-type impurity diffusion process]
The method for manufacturing a semiconductor substrate may further include a step of diffusing p-type impurities into the semiconductor substrate after the second etching step (hereinafter also referred to as “p-type impurity diffusion step”).

  When the p-type impurity diffusion step is performed, an oxide film remains in a region of the semiconductor substrate where the n-type diffusion layer is formed, and functions as a barrier layer against p-type impurity diffusion. For this reason, the diffusion of the p-type impurity to the region where the n-type diffusion layer is formed is effectively suppressed.

  An acceptor element can be used as the p-type impurity. An acceptor element means an element that can form a p-type diffusion layer by doping into a semiconductor substrate. As the acceptor element, a Group 13 element can be used, and examples thereof include boron (B), aluminum (Al) gallium (Ga), and indium (In). From the viewpoint of raw material price and versatility, the acceptor element is preferably at least one selected from the group consisting of boron and aluminum.

Examples of the acceptor element diffusion source include a gas containing an acceptor element such as boron tribromide (BBr ₃ ) and boron trichloride (BCl ₃ ), and a composition containing the acceptor element.
As a method for performing p-type impurity diffusion using a gas containing an acceptor element, for example, a diffusion gas such as BBr ₃ is introduced into a heated diffusion furnace to diffuse and deposit the acceptor element on the surface of the n-type semiconductor substrate. A method is mentioned.

  As a method for performing p-type impurity diffusion using a composition containing an acceptor element, for example, a composition containing an acceptor element is applied to a semiconductor substrate, and then the acceptor element is diffused into the semiconductor substrate in a heated diffusion furnace. A method is mentioned. The method for applying the composition containing the acceptor element to the semiconductor substrate is not particularly 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.

[Third etching step]
In the method for manufacturing a semiconductor substrate, after the p-type impurity diffusion step, the step of removing the oxide film in the region where the n-type diffusion layer of the semiconductor substrate is formed by etching (hereinafter also referred to as “third etching step”). May further be included. When a layer containing an acceptor element is formed on a semiconductor substrate in the p-type impurity diffusion step, the layer may be removed in this step.

  As an etching method in the third etching step, a known method such as a method using hydrofluoric acid, hydrofluoric acid, or the like can be applied.

<Solar cell element>
A solar cell element according to an embodiment of the present invention includes a semiconductor substrate having an n-type diffusion layer formed using the n-type diffusion layer forming composition described above, and an electrode provided on the semiconductor substrate having the n-type diffusion layer. And having. In this solar cell element, even if the p-type diffusion layer is formed on the same surface as the n-type diffusion layer of the semiconductor substrate, the diffusion of p-type impurities into the n-type diffusion layer is suppressed, and the semiconductor characteristics Deterioration of is suppressed. Therefore, it is suitably used not only as a solar cell element of a double-sided solar cell in which electrodes are provided on both sides but also as a solar cell element of a back-side electrode type solar cell in which electrodes are provided only on the back surface.

  The material and forming method of the electrode are not particularly limited, and for example, the material and forming method used in the method for manufacturing a solar cell element described later can be applied.

<Method for producing solar cell element>
The manufacturing method of the solar cell element of the embodiment of this invention includes the process of providing an electrode on the semiconductor substrate which has an n-type diffused layer mentioned above. According to this manufacturing method, even if the p-type diffusion layer is formed on the same surface as the surface on which the n-type diffusion layer of the semiconductor substrate is formed, the diffusion of p-type impurities into the n-type diffusion layer is suppressed, and the semiconductor Deterioration of characteristics is suppressed. Therefore, it can be suitably used not only as a solar cell element of a double-sided solar cell but also as a method of manufacturing a solar cell element of a back electrode solar cell.

According to the method for manufacturing a solar cell element, the step of forming the electrode can be performed separately from the step of forming the n-type diffusion layer. For this reason, there exists a tendency for the choices, such as an electrode material and a formation method, to spread.
The material and forming method of the electrode are not particularly limited, and materials and forming methods known in the art can be adopted. The material of the electrode is not limited to Group 13 aluminum used in the prior art, and Ag (silver), Cu (copper), etc. can be applied, and the thickness of the electrode is also thinner than the conventional one. It becomes possible to form.

  Since the semiconductor substrate having an n-type diffusion layer used in the above manufacturing method is manufactured using the above-described n-type diffusion layer forming composition, the n-type diffusion layer is selectively formed in a desired portion of the semiconductor substrate. Has been.

In the gas phase reaction method that has been widely adopted conventionally, it is necessary to convert an unnecessary n-type diffusion layer formed in a region other than a desired site into a p-type diffusion layer. As this conversion method, an n-type diffusion layer formed in a region other than a desired portion is applied with a paste of aluminum which is a Group 13 element and heat-treated, and aluminum is diffused into the n-type diffusion layer to form a p-type diffusion layer. The conversion method is adopted. In this method, conversion to the p-type diffusion layer is sufficient, and in order to form a high-concentration electric field layer of the p ⁺ -type diffusion layer, a certain amount of aluminum is required. There was a need to form. However, since the thermal expansion coefficient of aluminum is significantly different from the thermal expansion coefficient of the semiconductor substrate, a large internal stress is generated in the semiconductor substrate during the heat treatment and cooling, causing the warpage of the semiconductor substrate.

  This internal stress damages the crystal grain boundary when crystalline silicon is used as the semiconductor substrate, and there is a problem that power loss increases in a solar cell using this semiconductor substrate. Further, the warpage of the semiconductor substrate easily damages the solar cell element when the solar cell element is transported in the module process and when it is connected to a copper wire called a tab wire. In recent years, the thickness of a silicon substrate, which is a semiconductor substrate, is being reduced due to the improvement of slicing technology, and the solar cell element tends to be easily broken.

However, in the method for manufacturing a solar cell element of the present invention, since a semiconductor substrate having an n-type diffusion layer in which an n-type diffusion layer is formed in a desired portion is used, other than the desired portion that has been performed by the conventional method. Side etching or the like for removing the n-type diffusion layer formed on the substrate becomes unnecessary, and the process tends to be simplified. Further, the step of converting the n-type diffusion layer formed in a region other than the desired portion into the p ⁺ -type diffusion layer is not necessary, and the necessity of increasing the thickness of the aluminum layer is eliminated. As a result, generation of internal stress in the semiconductor substrate and warpage of the semiconductor substrate can be suppressed. As a result, it is possible to suppress an increase in power loss and damage of the solar battery cell in the solar battery using this semiconductor substrate.
As a result, the method for forming the p ⁺ -type diffusion layer, the material, shape, thickness, etc. of the electrode are not limited to the conventional methods, and there are tendencies to expand the choices of manufacturing method, material, shape, etc. to be applied.

  Next, a method for manufacturing a semiconductor substrate having an n-type diffusion layer and a method for manufacturing a solar cell element will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view conceptually showing an example of steps of a method for manufacturing a semiconductor substrate having an n-type diffusion layer and a method for manufacturing a solar cell element. In addition, the same code | symbol is attached | subjected to a common component.

  First, as shown in FIG. 1A, an alkaline solution is applied to a crystalline silicon substrate which is an n-type semiconductor substrate 1 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 20% by mass caustic soda. Next, etching is performed using a mixed solution of 1% by mass caustic soda and 10% by mass isopropyl alcohol to form a textured structure (in FIG. 1 (1), only one side of the n-type semiconductor substrate 1 has a description of the textured structure) To do). In the solar cell element, by forming a texture structure on the light receiving surface (the lower surface in FIG. 1 (1)), the light confinement effect is promoted, and high efficiency is achieved.

  Next, as shown in FIG. 1 (2), by partially applying the n-type diffusion layer forming composition to the back surface of the n-type semiconductor substrate 1, that is, the surface opposite to the light-receiving surface. Then, the n-type diffusion layer forming composition layer 2 is formed.

  Next, the n-type semiconductor substrate 1 on which the n-type diffusion layer forming composition layer 2 is formed is subjected to heat treatment (heat) at a temperature of 600 ° C. to 1200 ° C. and a gas flow rate of 3 mm / second to 60 mm / second at a linear velocity. Spread. By this heat treatment, the donor element contained in the n-type diffusion layer forming composition layer 2 is diffused into the n-type semiconductor substrate 1 to form the n-type diffusion layer 3. At this time, a glass layer (not shown) such as phosphate glass is formed on the surface of the n-type diffusion layer 3.

  After the heat treatment, the n-type semiconductor substrate 1 is cooled to room temperature. Thereafter, the glass layer formed on the n-type semiconductor substrate 1 is removed by etching (first etching).

  Next, oxidation treatment is performed to form the oxide film 4 on the n-type semiconductor substrate 1. As shown in FIG. 1 (3), the oxide film 4 is formed thick in the region where the n-type diffusion layer 3 is formed, and thin in the other regions.

  Next, the oxide film 4 in a region other than the region where the n-type diffusion layer 3 is formed is removed by etching (second etching). At that time, the oxide film 4 other than the region where the n-type diffusion layer 3 is formed is sufficiently removed, and the oxide film 4 in the region where the n-type diffusion layer 3 is formed is etched at a stage where the oxide film 4 is not partially removed. Stop. As a result, as shown in FIG. 1D, an n-type semiconductor substrate is obtained in which the oxide film 4 remains in the region where the n-type diffusion layer 3 is formed.

  Next, a boron silicate glass layer 5 is formed on the n-type semiconductor substrate 1 and the remaining oxide film 4, and boron is diffused to form a p-type diffusion layer 6. As shown in FIG. 1 (5), boron is diffused from the boron silicate glass layer 5 to form a p-type diffusion layer 6 in a region where the oxide film 4 does not remain on the n-type semiconductor substrate 1. The On the other hand, in the region where the oxide film 4 remains, the oxide film 4 functions as a barrier layer that suppresses boron diffusion. As a result, boron diffusion to the n-type diffusion layer 3 below the oxide film 4 is suppressed.

  Thereafter, the boron silicate glass layer 5 and the oxide film 4 are removed by etching (third etching), and the n-type diffusion layer 3 and the p-type diffusion layer 6 are provided on the back surface as shown in FIG. An n-type semiconductor substrate 1 is obtained.

  Next, the passivation film 7 and the antireflection film 9 are formed on the light receiving surface of the n-type semiconductor substrate 1, and the electrode 8 is further provided, whereby the solar cell element shown in FIG.

  In the above, the manufacturing method of the back surface electrode type (back contact type) solar cell element provided with the n type diffusion layer 3 and the p type diffusion layer 6 on the back surface of the n type semiconductor substrate 1 has been described. However, the above method can also be applied to a double-sided electrode type solar cell element.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. Unless otherwise stated, chemicals used reagents. “%” Means “% by mass” unless otherwise specified.

<Example 1>
4.5 g of P ₂ O ₅ —SiO ₂ —MgO glass (P ₂ O ₅ : 34%, SiO ₂ : 39%, MgO: 27%) particles having an average particle diameter of 1 μm, 1.5 g of ethyl cellulose, and weight A paste-like n-type diffusion layer forming composition was prepared by mixing 0.03 g of polymethylphenylsiloxane having an average molecular weight of 10,000 and 13.7 g of terpineol.
Next, the prepared n-type diffusion layer forming composition was applied to an n-type silicon substrate at 1 mg / cm ² by screen printing and dried on a hot plate at 150 ° C. for 5 minutes. Next, it was kept in an oven set at 450 ° C. for 1.5 minutes to remove ethyl cellulose.

  Subsequently, the silicon substrate coated with the n-type diffusion layer forming composition was placed in a diffusion furnace set at 950 ° C., and heat diffusion treatment was performed by holding for 20 minutes. At that time, a mixed gas of nitrogen and oxygen (nitrogen: oxygen volume ratio = 50: 50) was flowed into the diffusion furnace at a linear velocity of 3 mm / second. Thereafter, the silicon substrate was taken out from the diffusion furnace.

  The transparent glass layer was formed in the area | region which apply | coated the n type diffused layer formation composition of the taken out silicon substrate. In order to remove this glass layer, the silicon substrate was immersed in hydrofluoric acid for 5 minutes, washed with running water, and naturally dried.

  Thereafter, dry oxidation treatment was performed on the obtained silicon substrate by the following method. First, the diffusion furnace was heated to 1000 ° C. with 10 L of oxygen flowing, and the silicon substrate was placed in the diffusion furnace and left for 3 hours.

  A bluish silicon oxide film was formed in a region of the silicon substrate taken out from the diffusion furnace where the n-type diffusion layer forming composition was applied. When this silicon oxide film was observed with an optical microscope having a magnification of 100, the thickness of the silicon oxide film was sufficiently uniform.

<Example 2>
A silicon oxide film was formed in the same manner as in Example 1 except that the amount of the silicone compound in the n-type diffusion layer forming composition was 0.3 g. A bluish silicon oxide film was formed in the region of the silicon substrate where the n-type diffusion layer forming composition was applied. When this silicon oxide film was observed with an optical microscope having a magnification of 100, the thickness of the silicon oxide film was sufficiently uniform.

<Example 3>
A silicon oxide film was formed in the same manner as in Example 1 except that the weight average molecular weight of the silicone compound in the n-type diffusion layer forming composition was 100,000. A bluish silicon oxide film was formed in a region where the composition for forming an n-type diffusion layer of the obtained silicon substrate was applied. When this silicon oxide film was observed with an optical microscope having a magnification of 100, the thickness of the silicon oxide film was sufficiently uniform.

<Comparative Example 1>
A silicon oxide film was formed in the same manner as in Example 1 except that no silicone compound was added to the n-type diffusion layer forming composition. Although it was confirmed by visual observation that a bluish silicon oxide film was formed in a region where the n-type diffusion layer forming composition of the obtained silicon substrate was applied, this silicon oxide film was optically magnified 100 times. When observed with a microscope, countless white regions having a size of 1 μm to 5 μm were observed. When this white region was observed with an electron microscope, it was found that the silicon oxide film was a very thin region, and it was determined that the thickness of the obtained silicon oxide film was non-uniform.

1 n-type semiconductor substrate 2 n-type diffusion layer forming composition layer 3 n-type diffusion layer 4 silicon oxide film 5 boron silicate layer 6 p-type diffusion layer 7 passivation film 8 electrode 9 antireflection film

Claims (8)

  An n-type diffusion layer forming composition containing glass particles containing a donor element, a dispersion medium, and a silicone compound.   The n-type diffusion layer forming composition according to claim 1, wherein the donor element is at least one selected from the group consisting of P (phosphorus) and Sb (antimony). The glass particles containing the donor element include at least one donor element-containing material selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ ; and SiO ₂ , K ₂ O, Na ₂ O At least one glass component material selected from the group consisting of Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ and MoO _3. The n-type diffused layer formation composition of Claim 1 or Claim 2 to contain.   The n-type diffusion layer forming composition according to any one of claims 1 to 3, wherein the silicone compound has a weight average molecular weight of 1,000 to 100,000.   The semiconductor substrate which has an n-type diffused layer formed using the n-type diffused layer formation composition of any one of Claims 1-4.   A step of forming an n-type diffusion layer forming composition layer by applying the n-type diffusion layer forming composition according to any one of claims 1 to 4 to at least a part of at least one surface of a semiconductor substrate. And a step of heat-treating the n-type diffusion layer forming composition layer to form an n-type diffusion layer.   A semiconductor substrate having an n-type diffusion layer formed using the n-type diffusion layer forming composition according to any one of claims 1 to 4, and an electrode provided on the semiconductor substrate. Solar cell element.   Manufacture of a solar cell element including a step of providing an electrode on a semiconductor substrate having an n-type diffusion layer formed using the n-type diffusion layer forming composition according to any one of claims 1 to 4. Method.