JP2017028122A - N-type diffusion layer forming composition, method for manufacturing semiconductor substrate with n-type diffusion layer, method for manufacturing solar cell element, and solar cell element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an n-type diffusion layer forming composition in which an n-type diffusion layer with suppressed variations of sheet resistance can be formed, a method for forming a semiconductor substrate with an n-type diffusion layer using the same, a method for manufacturing a solar cell element using the same, and a solar cell element.SOLUTION: An n-type diffusion layer forming composition includes a glass particle containing a donor element and at least one kind selected from the group consisting of Te, Sn, Zn, V, and Bi, and a dispersion medium.SELECTED DRAWING: None

Description

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

The manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate in which a texture structure is formed on a surface to be a light receiving surface of a solar cell is prepared so as to promote the light confinement effect and increase the efficiency. Subsequently, a phosphorous silicate glass (PSG) layer is uniformly formed by performing several tens of minutes at 800 ° C. to 900 ° C. in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), which is a donor element-containing compound, and nitrogen and oxygen. Form. Phosphorus diffuses from the PSG layer into the silicon substrate, forming an n-type diffusion layer. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the surface but also on the side surface and the back surface. Therefore, a side etching process for removing the side n-type diffusion layer is necessary. Further, the n-type diffusion layer on the back surface needs to be converted into a p ⁺ -type diffusion layer. An aluminum paste is applied on the n-type diffusion layer on the back surface, and the p ⁺ -type diffusion is performed from the n-type diffusion layer by the diffusion of aluminum. Was converted into a layer.

On the other hand, for forming an n-type diffusion layer, a paste-like n-type diffusion layer forming composition containing glass particles containing phosphorus as a donor element is applied to the surface of a silicon substrate and thermally diffused to form a diffusion layer. The technique of doing is also known (for example, refer patent document 1). In this case, the glass particles are softened and melted at a high temperature during the diffusion treatment, and spread uniformly on the silicon substrate. As a result, a molten glass layer such as a PSG layer formed in the above-described POCl ₃ diffusion is formed on the silicon substrate, and phosphorus diffuses from the molten glass layer to the silicon substrate to form an n-type diffusion layer.

Japanese Patent No. 5176159

  In the method described in Patent Document 1, when the glass particles containing phosphorus as a donor element have a high softening point, some glass particles are not melted even in a temperature region where phosphorus diffusion starts during diffusion treatment. May remain in the state. In that case, a region covered with molten glass and a region not covered with molten glass coexist on the silicon substrate. If so, phosphorus diffusion is started first from the region covered with the molten glass, and the start of phosphorus diffusion to the region not covered with the molten glass is delayed. As a result, the amount of phosphorus diffused into the silicon substrate may be uneven, and the variation in sheet resistance of the formed n-type diffusion layer may increase.

  If the unevenness of the phosphorus diffusion amount to the silicon substrate can be suppressed, an n-type diffusion layer in which variation in sheet resistance is suppressed can be formed, and an improvement in the characteristics of the solar cell can be expected. Therefore, the present invention provides an n-type diffusion layer forming composition capable of forming an n-type diffusion layer in which variation in sheet resistance is suppressed, a method for forming an n-type diffusion layer using the same, and a solar cell using the same An element and a manufacturing method thereof are provided.

<1> An n-type diffusion layer forming composition comprising glass particles containing a donor element and at least one selected from the group consisting of Te, Sn, Zn, V and Bi, and a dispersion medium.
<2> The n-type diffusion layer forming composition according to claim 1, wherein at least one selected from the group consisting of Te, Sn, Zn, V and Bi contains Te.
<3> The glass particles have a ratio of at least one selected from the group consisting of TeO ₂ , SnO, ZnO, V ₂ O ₅ and Bi ₂ O _{3 in} terms of oxides of 3 mol% or more of the entire glass particles. The n-type diffusion layer forming composition according to <1> or <2>.
<4> The n-type diffusion layer forming composition according to any one of <1> to <3>, wherein the glass particles further include at least one selected from the group consisting of Ca and Mg.
<5> The n-type diffusion layer forming composition according to any one of <1> to <4>, wherein the glass particles further contain Si.
<6> The n-type diffusion layer forming composition according to any one of <1> to <5>, further including a silane compound.
<7> The n-type diffusion layer forming composition according to <6>, wherein the silane compound includes N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane.
<8> The n-type diffusion layer forming composition according to any one of <1> to <7>, wherein the glass particles have a volume average particle diameter of 10 μm or less.
<9> The n-type diffusion layer forming composition according to any one of <1> to <8>, wherein the content of the glass particles is 1% by mass to 30% by mass.
<10> The n-type diffusion layer forming composition according to any one of <1> to <9>, wherein the dispersion medium includes at least one selected from the group consisting of terpineol and butyl carbitol acetate.
<11> The n-type diffusion layer forming composition according to any one of <1> to <10>, wherein the dispersion medium contains ethyl cellulose.
<12> A step of applying the n-type diffusion layer forming composition according to any one of <1> to <11> on a semiconductor substrate, and a semiconductor provided with the n-type diffusion layer forming composition And a step of forming an n-type diffusion layer by subjecting the substrate to a thermal diffusion treatment.
<13> A step of applying the n-type diffusion layer forming composition according to any one of <1> to <11> on a semiconductor substrate, and a semiconductor provided with the n-type diffusion layer forming composition A method for manufacturing a solar cell element, comprising: a step of performing a thermal diffusion treatment on a substrate to form an n-type diffusion layer; and a step of forming an electrode on the n-type diffusion layer.
<14> A solar cell element obtained by the production method according to <13>.

  According to the present invention, an n-type diffusion layer forming composition capable of forming an n-type diffusion layer with suppressed variation in sheet resistance, a method for forming a semiconductor substrate with an n-type diffusion layer using the same, and A method for manufacturing a solar cell element and a solar cell element used are provided.

It is sectional drawing which shows notionally an example of the manufacturing process of the solar cell element of this invention. It is the top view which looked at the solar cell element from the surface. It is a perspective view which expands and shows a part of FIG. 2A.

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 the term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. .
Moreover, the numerical value range shown using "to" shows the range which includes the numerical value described before and behind "to" as a minimum value and a maximum value, respectively.
Further, the amount of each component in the composition means the total amount of the plurality of types of substances present in the composition unless there is a specific indication when there are a plurality of types of substances corresponding to the respective components in the composition. . 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
Further, 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 not only a configuration of a shape formed over the entire surface but also a configuration of a shape formed in part when observed as a plan view. Is done.

<N-type diffusion layer forming composition>
An n-type diffusion layer forming composition according to an embodiment of the present invention includes glass particles containing a donor element and at least one selected from the group consisting of Te, Sn, Zn, V, and Bi, a dispersion medium, including. According to the composition for forming an n-type diffusion layer, an n-type diffusion layer in which variation in sheet resistance is suppressed can be formed on a semiconductor substrate. The reason is not clear, but is presumed as follows.

  At least one selected from the group consisting of Te, Sn, Zn, V and Bi (hereinafter also referred to as “specific element”) plays a role of lowering the softening point of the glass when incorporated into the glass. For this reason, glass particles can be melted at a temperature lower than the temperature at which the diffusion of the donor element starts by containing the specific element in the glass particles. For this reason, it becomes easy to make it the state where the area | region which provided the n type diffused layer formation composition of the semiconductor substrate at the time of the spreading | diffusion of a donor element was covered with the layer of the molten glass. When the surface of the semiconductor substrate is covered with the glass layer, a region where the glass and the semiconductor substrate are in contact with each other increases, and the diffusion of the donor element from the inside of the glass to the semiconductor substrate is easily performed without unevenness. As a result, it is considered that an n-type diffusion layer in which the variation in sheet resistance is suppressed is easily formed in the region of the semiconductor substrate to which the n-type diffusion layer forming composition is applied.

(Glass particles)
The glass particles contained in the n-type diffusion layer forming composition contain a donor element and at least one selected from the group consisting of Te, Sn, Zn, V, and Bi. In the present specification, the glass particles mean particles in which glass (an amorphous solid exhibiting a glass transition phenomenon) is formed into particles.

  The presence of the donor element in the glass particles suppresses the donor element in the glass particles from being volatilized outside during the heat treatment. For this reason, it is suppressed that a donor element volatilizes and an n-type diffused layer is formed even in the back surface or side surface of a semiconductor substrate. Therefore, by using an n-type diffusion layer forming composition containing glass particles containing a donor element, an n-type diffusion layer is not formed on the back surface, side surface, etc. of the semiconductor substrate, and n can be selectively formed at a desired site. A mold diffusion layer can be formed.

  If the composition for forming an n-type diffusion layer containing glass particles is applied, the side etching step that has been conventionally performed by a widely employed gas phase reaction method becomes unnecessary, and the process tends to be simplified. 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.

(Donor element)
The donor element means an element that can form an n-type diffusion layer in the semiconductor substrate. As the donor element, for example, an element belonging to Group 15 can be used. Examples of the Group 15 element 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), and contains P (phosphorus). More preferred.

Examples of the substance (donor element-containing substance) used for introducing the donor element into the glass particles include P ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ and As ₂ O ₃ , and among them, 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 content of the donor element in the glass particles is not particularly limited. For example, from the viewpoint of sufficiently forming the n-type diffusion layer, when the components of the glass particles are converted into oxides, the donor element oxides (P ₂ O ₅ , Sb ₂ O ₃ , As ₂ O _3, etc.) The ratio is preferably 20 mol% or more, more preferably 25 mol% or more of the entire glass particles. From the viewpoint of balance with other components, for example, the ratio of the donor element oxide in terms of oxide is preferably 50 mol% or less, more preferably 40 mol% or less of the entire donor glass particle. . In particular, when the donor element contains highly hygroscopic phosphorus, the moisture content of the glass particles can be kept low by setting the content to the above range.

(Specific element)
The specific element contained in the glass particles is at least one selected from the group consisting of Te, Sn, Zn, V, and Bi. Te is preferable from the viewpoints of the effect of lowering the softening point of the glass particles, the handleability, and the like.

Examples of the substance (specific element-containing substance) used for introducing the specific element into the glass particles include TeO ₂ , SnO, ZnO, V ₂ O ₅ and Bi ₂ O ₃ , and TeO ₂ is particularly preferable.

The content of the specific element in the glass particles is not particularly limited. For example, from the viewpoint of effectively lowering the softening point of the glass particles, when the components of the glass particles are converted into oxides, specific element oxides (TeO ₂ , SnO, ZnO, V ₂ O ₅ and Bi ₂ O _{3 are used.} ) Is preferably 3 mol% or more, more preferably 5 mol% or more of the total donor glass particles. From the viewpoint of balance with other components, for example, the ratio of the specific element oxide in terms of oxide is preferably 40 mol% or less, and more preferably 30 mol% or less of the entire glass particle.

(Other elements)
The glass particles may contain other elements other than the donor element and the specific element. Examples of other elements include Si, Ca, Mg, K, Na, Li, Ba, Sr, Be, Pb, Cd, Zr, Mo, La, Nb, Ta, Y, Ti, Ge, Al, and Lu. Can be mentioned.

Examples of substances (glass component substances) used for introducing other elements into glass particles include SiO ₂ , CaO, MgO, K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, BeO, PbO, _{CdO, ZrO 2, MoO 3,} La 2 O 3, Nb 2 O 5, Ta 2 O 5, Y 2 O 3, TiO 2, GeO 2, Al 2 O 3 and _Lu 2 _{O 3} and the like.

  The glass particles may contain Si as another element. When the glass particles contain Si, when etching with hydrofluoric acid for removing the glass layer formed on the semiconductor substrate is performed, the removability of the glass layer is improved and the generation of residues is suppressed.

When the glass particles contain Si, the content is not particularly limited. For example, from the viewpoint of removability of the glass layer, the ratio of SiO ₂ in terms of oxide is preferably 30 mol% or more, more preferably 40 mol% or more of the entire glass particles. From the viewpoint of keeping the softening point of the glass particles low, the ratio of SiO ₂ in terms of oxide is preferably 70 mol% or less, more preferably 60 mol% or less of the entire glass particles.

  The glass particles may contain at least one selected from the group consisting of Ca and Mg as other elements. When the glass particles contain at least one selected from the group consisting of Ca and Mg, it is possible to suppress moisture absorption of the glass particles when phosphorus having high hygroscopicity is used as the donor element.

  When the glass particles contain at least one selected from the group consisting of Ca and Mg, the content is not particularly limited. For example, from the viewpoint of obtaining a sufficient moisture absorption suppressing effect, the proportion of at least one selected from the group consisting of CaO or MgO in terms of oxide is preferably 2 mol% or more of the entire glass particles, and 5 mol % Or more is more preferable. From the viewpoint of keeping the softening point of the glass low, for example, the ratio of at least one selected from the group consisting of CaO or MgO in terms of oxide is preferably 30 mol% or less of the entire glass particles, and 25 mol % Or less is more preferable.

  When the glass particles contain other elements, from the viewpoints of moisture resistance and melting temperature of the glass particles, etching removal of the glass layer, diffusibility of the donor element, etc., for example, other elements in terms of oxides The ratio of the glass component substance to be contained can be 0.01 mol% to 10 mol%, and preferably 0.1 mol% to 5 mol% of the entire glass particles.

  The softening point of the glass particles is preferably lower than the diffusion temperature of the donor element contained in the glass particles (the temperature at which the donor element begins to diffuse into the semiconductor substrate). In this case, the glass particles are melted before the diffusion of the donor element is started, and the region to which the n-type diffusion layer forming composition of the semiconductor substrate is applied is easily covered with the molten glass. The softening point of the glass particles can be obtained from a differential heat (DTA) curve or the like using a differential heat / thermogravimetric simultaneous measurement apparatus (for example, DTG-60H type manufactured by Shimadzu Corporation).

  The softening point of the glass particles suppresses the formation of an n-type diffusion layer other than a specific portion by suppressing the occurrence of dripping by preventing the viscosity of the molten glass from being too low during the diffusion process of the donor element. For example, the temperature is preferably 200 ° C. or higher, and more preferably 300 ° C. or higher, from the viewpoint of facilitating.

  The softening point of the glass particles is, for example, 550 ° C. or less from the viewpoint of easily forming the n-type diffusion layer in which the glass particles are sufficiently melted before the donor element diffuses and the variation in sheet resistance is suppressed. The temperature is preferably 500 ° C. or lower, more preferably 450 ° C. or lower.

  The shape of the glass particles is not particularly limited. For example, substantially spherical shape, flat shape, block shape, plate shape, and scale shape are mentioned. From the viewpoint of applicability (coating property) to a semiconductor substrate and non-uniform diffusibility when an n-type diffusion layer forming composition is used, it is preferably substantially spherical, flat or plate-like.

The size of the glass particles is not particularly limited. For example, from the viewpoint of facilitating smoothing of the molten glass layer, the volume average particle diameter is preferably 10 μm or less, more preferably 5 μm or less, further preferably 2 μm or less, and 1 μm or less. It is particularly preferred. The lower limit of the volume average particle diameter of the glass particles is not particularly limited, but is preferably 0.01 μm or more, and more preferably 0.05 μm or more, for example.
Here, the volume average particle diameter of the glass particles is a value measured by a laser scattering diffraction particle size distribution measuring apparatus or the like, and is a particle diameter (D50%) corresponding to 50% of the volume accumulation from the small diameter side.

The method for producing the glass particles according to the present invention is not particularly limited. For example, it is produced by the following procedure.
First, weigh the ingredients and fill the crucible. Examples of the crucible material include platinum, platinum-rhodium, gold, iridium, alumina, zirconia, quartz, carbon, boron carbide, boron nitride, and silicon nitride. The material of the crucible is appropriately selected in consideration of the melting temperature, atmosphere, reactivity with the molten material, and the like. Next, the raw material is heated at a temperature corresponding to the glass composition in an electric furnace to obtain a melt. At this time, it is desirable to stir the melt uniformly. Subsequently, the obtained melt is poured onto a zirconia substrate, a carbon substrate or the like to vitrify the melt. Finally, the glass is crushed into particles. A known method such as a stamp mill, a jet mill, a bead mill, or a ball mill can be applied to the pulverization.

  The content of the glass particles in the n-type diffusion layer forming composition is determined in consideration of the suitability for application, the diffusibility of the donor element, and the like. In general, the content of the glass particles is preferably in the range of 1% by mass to 30% by mass of the total mass of the n-type diffusion layer forming composition, and more preferably in the range of 5% by mass to 25% by mass. Preferably, it is still more preferably in the range of 8% by mass to 20% by mass.

(Dispersion medium)
The dispersion medium is a medium in which the glass particles are dispersed in the composition. As the dispersion medium, for example, at least one selected from the group consisting of a binder and a solvent can be used.

  Examples of the binder include polyvinyl alcohol, polyacrylamide resin, polyvinyl amide resin, polyvinyl pyrrolidone, polyethylene oxide resin, polysulfonic acid, acrylamide alkyl sulfonic acid, cellulose ether resin, cellulose derivative, carboxymethyl cellulose, hydroxyethyl cellulose, ethyl cellulose, gelatin, starch And starch derivatives, sodium alginates and sodium alginate derivatives, xanthan and xanthan derivatives, gua and guar derivatives, scleroglucan and scleroglucan derivatives, tragacanth and tragacanth derivatives, dextrin and dextrin derivatives, (meth) acrylic acid resin, (meta) ) Acrylic ester resin (alkyl (meth) acrylate resin, dimethylamino Ethyl (meth) acrylate resin, etc.), butadiene resins, styrene resins, and copolymers thereof. In addition, a siloxane resin or the like can be appropriately selected. These binders may be used alone or in combination of two or more. As the binder, ethyl cellulose is particularly preferable in terms of viscosity characteristics.

  The weight average molecular weight of the binder is not particularly limited, and is preferably adjusted in consideration of the desired viscosity as the composition, the imparting characteristics during printing, and the like. The binder content in the n-type diffusion layer forming composition is, for example, preferably in the range of 1 Pa · s to 500 Pa · s, and more preferably in the range of 10 Pa · s to 100 Pa · s. The viscosity is measured using an E-type viscometer EHD type manufactured by Tokyo Keiki Co., Ltd. under the conditions of a sample amount of 0.4 ml and a rotation speed of 5 times / minute (rpm).

  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 dipropyl ketone, di-isobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n-propyl ether , Di-isopropyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol Cold di-n-propyl ether, ethylene glycol dibutyl ether, 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 Glico 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- 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 Rumethyl-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, tetra Propylene glycol methyl-n-butyl ether, tetrapropylene Ether solvents such as recall di-n-butyl ether, tetrapropylene glycol methyl-n-hexyl ether, tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate S-butyl acetate, n-pentyl acetate, s-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, Cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, acetic acid diethylene glycol methyl ether, acetic acid diethylene glycol monoethyl ether, acetic acid diethylene glycol monobutyl ether, Dipropylene glycol methyl ether, dipropylene glycol ethyl ether acetate, diacetic acid glycol, methoxytriethylene glycol acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, 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-butyrolactone, γ-valerolactone, etc. Ester solvent: acetonitrile, N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, N , N-dimethyl sulfoxide and other aprotic polar solvents; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, s-butanol, t-butanol, n-pentanol, isopentanol, 2-methyl Butanol, s-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, s-hexanol, 2-ethylbutanol, s-heptanol, n-octanol, 2-ethane Tylhexanol, s-octanol, n-nonyl alcohol, n-decanol, s-undecyl alcohol, trimethylnonyl alcohol, s-tetradecyl alcohol, s-heptadecyl alcohol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and other alcohol solvents; phenol and other phenol solvents; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether Diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriethylene glycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol Examples include glycol monoether solvents such as monomethyl ether; terpene solvents such as terpinene, terpineol, myrcene, alloocimene, limonene, dipentene, pinene, carvone, ocimene, and ferrandrene; water and the like. These solvents may be used alone or in combination of two or more.

  From the viewpoint of suitability for application to a semiconductor substrate, the solvent is preferably at least one selected from the group consisting of terpineol and butyl carbitol acetate (diethylene glycol mono-n-butyl ether acetate). The content ratio of the dispersion medium in the n-type diffusion layer forming composition is determined in consideration of application suitability, donor concentration, and the like.

  When the n-type diffusion layer forming composition contains a dispersion medium, the content is not particularly limited. The content of the dispersion medium in the n-type diffusion layer forming composition is, for example, preferably 60% by mass to 95% by mass, and more preferably 70% by mass to 90% by mass.

(Silane compound)
The n-type diffusion layer forming composition may contain a silane compound. In general, glass particles containing P ₂ O ₅ , TeO ₂ or the like as components have high hygroscopicity, but the hygroscopicity can be suppressed low by containing a silane compound. Therefore, when the silane compound is contained in the n-type diffusion layer forming composition, the moisture absorption of the glass particles is suppressed, the change in diffusion capacity is suppressed, and the n-type diffusion layer is easily formed stably.

  The kind of silane compound is not particularly limited. For example, the silane compound corresponding to the following (a)-(g) is mentioned.

(A) 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyldimethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, etc. Silane compound having (meth) acryloxy group (b) Epoxy group such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Or a silane compound having a glycidoxy group (c) a silane compound having an amino group such as N- (aminoethyl) 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc. (d) 3-mercaptopropyltri Silane compounds having a mercapto group such as toxisilane (e) Methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, Silane compounds having an alkyl group such as hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis (trimethoxysilyl) hexane (f) Phenyl groups such as phenyltrimethoxysilane and phenyltriethoxysilane (G) Silane compounds having a trifluoroalkyl group such as trifluoropropyltrimethoxysilane

  From the viewpoint of effectively suppressing the moisture absorption of the glass particles, the silane compound is preferably a silane compound having an amino group, and more preferably N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane. A silane compound may be used individually by 1 type, or may be used in combination of 2 or more types.

  When the n-type diffusion layer forming composition contains a silane compound, the content is not particularly limited. The content of the silane compound in the n-type diffusion layer forming composition is, for example, preferably 0.01% by mass to 5% by mass, and more preferably 0.1% by mass to 3% by mass.

  The method for producing the n-type diffusion layer forming composition is not particularly limited. For example, it can be obtained by mixing the above-described components by a known method.

<Method for manufacturing semiconductor substrate with n-type diffusion layer>
The method for producing a semiconductor substrate with an n-type diffusion layer according to an embodiment of the present invention includes a step of applying the above-described n-type diffusion layer forming composition on a semiconductor substrate (n-type diffusion layer forming composition applying step), and a step of performing a thermal diffusion treatment on the semiconductor substrate to which the n-type diffusion layer forming composition is applied to form an n-type diffusion layer (n-type diffusion layer forming step).

  The method for carrying out the n-type diffusion layer forming composition application step is not particularly limited. For example, 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 are exemplified. Among these, the printing method is preferable, and the screen printing method is more preferable.

  The method for performing the n-type diffusion layer forming step is not particularly limited. For example, a known continuous furnace or batch furnace can be applied. The temperature at which the thermal diffusion treatment is performed is not particularly limited as long as it is equal to or higher than the temperature at which the donor element diffuses into the semiconductor substrate. The temperature of the thermal diffusion treatment may be constant throughout the n-type diffusion layer forming process or may vary.

  From the viewpoint of suppressing the variation in sheet resistance of the n-type diffusion layer, the surface of the semiconductor substrate is covered with molten glass when the donor element in the n-type diffusion layer forming composition diffuses into the semiconductor substrate. It is preferable. Therefore, in the method of manufacturing a semiconductor substrate with an n-type diffusion layer, the step of softening glass particles by heating the n-type diffusion layer forming composition provided on the semiconductor substrate before the n-type diffusion layer forming step (glass It is preferable to have a particle softening step.

  The glass particle softening step is preferably performed at a temperature not higher than the diffusion temperature of the donor element and not lower than the softening point of the glass particles. For example, it is preferably performed within a range of 200 ° C to 500 ° C. The glass particle softening step may be performed under conditions such that all of the glass particles are softened, or may be performed under conditions such that a part of the glass particles remain as glass particles. From the viewpoint of suppressing the variation in sheet resistance of the n-type diffusion layer, it is preferable to carry out the conditions under which all the glass particles are softened.

  The kind of the semiconductor substrate is not particularly limited, and a normal one can be applied. 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 of the substrate include an indium phosphide substrate, a silicon carbide substrate, a silicon germanium substrate, and a copper indium selenium substrate. When used for a solar cell element, the semiconductor substrate is preferably a silicon substrate, a germanium substrate, or a silicon carbide substrate, and more preferably a silicon substrate.

<Method for producing solar cell element>
The method for manufacturing a solar cell element according to an embodiment of the present invention includes a step of applying the n-type diffusion layer forming composition described above on a semiconductor substrate (n-type diffusion layer forming composition applying step), and n-type diffusion layer formation. Forming a n-type diffusion layer by applying a thermal diffusion treatment to the semiconductor substrate to which the composition is applied (n-type diffusion layer forming step), and forming an electrode on the formed n-type diffusion layer (electrode) Forming step).

  The manufacturing method of a solar cell element has the process (glass particle softening process) of heating the n-type diffusion layer forming composition provided on the semiconductor substrate and softening the glass particles before the n-type diffusion layer forming process. It is preferable.

  Details of the n-type diffusion layer forming composition application step, the glass particle softening step, and the n-type diffusion layer formation step are the n-type diffusion layer formation composition application step and n-type in the above-described method for manufacturing a semiconductor substrate with an n-type diffusion layer. This is the same as the details of the diffusion layer forming step.

Hereinafter, an embodiment of 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 a manufacturing process of a solar cell element. In FIG. 1, 10 is a p-type semiconductor substrate, 11 is an n-type diffusion layer forming composition layer, 12 is an n-type diffusion layer, 13 is a p-type diffusion layer forming composition layer, 14 is a p ⁺ -type diffusion layer, Reference numeral 16 denotes an antireflection film, 17 denotes a metal paste layer for a front electrode, 18 denotes a front electrode, 19 denotes a metal paste layer for a back electrode, and 20 denotes a back electrode (electrode layer). In the following, an example in which a silicon substrate is used as a p-type semiconductor substrate will be described. However, in the present invention, the semiconductor substrate is not limited to a silicon substrate.

  In FIG. 1A, an alkaline solution is applied to a silicon substrate which is a p-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 20% by mass caustic soda. 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 on the surface of the silicon substrate (the description of the texture structure is omitted in the figure). By forming the texture structure on the side that becomes the light receiving surface (surface) when the solar cell element is formed, the light confinement effect is promoted, and high efficiency is achieved.

In FIG. 1B, an n-type diffusion layer forming composition layer 11 is formed by applying an n-type diffusion layer forming composition to the surface of the p-type semiconductor substrate 10, that is, the surface that serves as a light receiving surface. The application method 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. Of these, the printing method is preferable, and the screen printing method is more preferable.
application amount of n-type diffusion layer forming composition is not particularly limited, for example, be a 0.01g ^{/ m 2} ~100g ^/ m 2 as the amount of glass ^{particles, 0.1g / m 2 ~10g / m} 2 It is preferable that

  When the n-type diffusion layer forming composition contains a solvent as a dispersion medium, the n-type diffusion layer forming composition was applied to remove at least a part of the solvent contained in the composition before the thermal diffusion treatment. There is a case where a process of heat-treating the subsequent p-type semiconductor substrate 10 is necessary. The heat treatment in this case is performed at a temperature of, for example, 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 heat treatment conditions depend on the type, composition, content, and the like of the solvent contained in the n-type diffusion layer forming composition, and are not particularly limited to the above conditions.

  When the n-type diffusion layer forming composition contains a binder as a dispersion medium, the n-type diffusion layer forming composition was applied to remove at least a part of the binder contained in the composition before the thermal diffusion treatment. There is a case where a process of heat-treating the subsequent p-type semiconductor substrate 10 is necessary. In this case, for example, the heat treatment is performed under a condition of treatment at a temperature exceeding 300 ° C. and not more than 800 ° C. for 1 to 10 minutes. A known continuous furnace, batch furnace or the like can be applied to this heat treatment. The heat treatment conditions depend on the type, composition, content, and the like of the binder contained in the n-type diffusion layer forming composition, and are not particularly limited to the above conditions.

  When the n-type diffusion layer forming composition contains a dispersion medium, depending on the type, composition, content, etc., the heat treatment at the temperature of 80 ° C. to 300 ° C. and the temperature of over 300 ° C. to 800 ° C. Both heat treatments may be performed (that is, heat treatment is performed twice under different temperature conditions), or only one of the heat treatments may be performed.

  In FIG. 1B, the p-type diffusion layer forming composition layer 13 is formed by applying the p-type diffusion layer forming composition to the back surface of the p-type semiconductor substrate 10, that is, the surface opposite to the light receiving surface. The application method 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. Of these, the printing method is preferable, and the screen printing method is more preferable.

As the p-type diffusion layer forming composition, for example, p-type diffusion layer formation is performed in the same manner as the n-type diffusion layer forming composition using glass particles containing an acceptor element instead of glass particles containing a donor element. A composition can be mentioned. Examples of the acceptor element include Group 13 elements such as B (boron), Al (aluminum), and Ga (gallium). Glass particles containing acceptor _element, B ₂ O 3, _Al preferably contains at least one selected from 2 _{O 3} and the group consisting of _Ga 2 _{O 3.}

The method for applying the p-type diffusion layer forming composition to the back surface of the p-type semiconductor substrate 10 is performed in the same manner as the method for applying the n-type diffusion layer forming composition to the light-receiving surface of the p-type semiconductor substrate 10 described above. be able to. The p-type semiconductor substrate 10 provided with the p-type diffusion layer forming composition on the back surface is subjected to a thermal diffusion process in the same manner as the thermal diffusion process in the n-type diffusion layer forming composition to be described later. A p ⁺ -type diffusion layer 14 can be formed on the back surface of the substrate. From the viewpoint of production efficiency, the thermal diffusion treatment for forming the p-type diffusion layer is preferably performed simultaneously with the thermal diffusion treatment for forming the n-type diffusion layer.

  After the n-type diffusion layer forming composition layer 11 is formed on the light receiving surface of the p-type semiconductor substrate 10 and the p-type diffusion layer forming composition layer 13 is formed on the back surface, the p-type semiconductor substrate 10 is subjected to thermal diffusion treatment. The temperature of the thermal diffusion treatment is preferably 800 ° C to 1000 ° C, and more preferably 850 ° C to 980 ° C. The treatment time is preferably 5 minutes to 60 minutes. By this thermal diffusion treatment, as shown in FIG. 1 (3), the donor element diffuses into the p-type semiconductor substrate 10 to form the n-type diffusion layer 12. In addition, the acceptor element diffuses to form the p-type diffusion layer 14. A known continuous furnace, batch furnace, or the like can be applied to the thermal diffusion treatment. Moreover, the atmosphere in the furnace at the time of the thermal diffusion treatment can be selected according to desired conditions from an inert gas such as air, oxygen, nitrogen, or a mixed gas thereof.

  A glass layer (not shown) such as phosphate glass is formed on the surface of the n-type diffusion layer 12 formed on the light receiving surface of the p-type semiconductor substrate 10. For this reason, this phosphate glass is removed by etching. As the etching, any of known methods such as a method of immersing in an acid such as hydrofluoric acid and a method of immersing in an alkali such as caustic soda can be applied. In terms of etching ability, an etching treatment with hydrofluoric acid is preferable. Examples of the etching treatment with hydrofluoric acid include a method of immersing the p-type semiconductor substrate 10 in hydrofluoric acid. When the p-type semiconductor substrate 10 is immersed in hydrofluoric acid, the immersion time is not particularly limited. Generally, it can be 0.5 minutes to 30 minutes, and preferably 1 minute to 10 minutes.

  In the method for forming an n-type diffusion layer of this embodiment shown in FIGS. 1 (2) and (3), an n-type diffusion layer 12 is formed at a desired site, and an unnecessary n-type diffusion layer is formed on the back surface and side surfaces. Not formed. Therefore, in the conventional method of forming an n-type diffusion layer by a gas phase reaction method, a side etching process for removing an unnecessary n-type diffusion layer formed on a side surface is essential. According to the manufacturing method of the invention, the side etching process is not required, and the process is simplified. Thus, according to the method of the present embodiment, an n-type diffusion layer having a desired shape and a desired shape, in which variation in sheet resistance is suppressed, is formed in a short time.

Further, in the conventional manufacturing method, it is necessary to convert an unnecessary n-type diffusion layer formed on the back surface into a p-type diffusion layer. As this conversion method, a group 13 element is added to the n-type diffusion layer on the back surface. A method is adopted in which an aluminum paste is applied and baked to diffuse aluminum into the n-type diffusion layer and convert it into a p-type diffusion layer. 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 that of silicon used as a substrate, a large internal stress is generated in the silicon substrate during the firing and cooling process, causing warpage of the silicon substrate. . This internal stress has a problem that the crystal grain boundary is damaged and the power loss increases. Further, the warpage easily damages the solar cell element in the transportation of the solar cell element in the module process and the connection with a copper wire called a tab wire (wiring member). In recent years, the thickness of the silicon substrate has been reduced due to the improvement of the slice processing technique, and the solar cell element tends to be easily broken.

  However, according to the method of the present embodiment, since an unnecessary n-type diffusion layer is not formed on the back surface, there is no need to convert from the n-type diffusion layer to the p-type diffusion layer, and it is necessary to increase the thickness of the aluminum layer. Disappear. As a result, generation of internal stress and warpage in the silicon substrate can be suppressed. As a result, increase in power loss and damage to the solar cell element can be suppressed.

Further, when the manufacturing method of the present invention is used, the manufacturing method of the p ⁺ -type diffusion layer (high concentration electric field layer) 14 on the back surface is limited to a method by conversion from an n-type diffusion layer to a p-type diffusion layer with aluminum. Any method can be adopted without any problem, and the choice of manufacturing method is expanded.
For example, as described above, a p-type diffusion layer forming composition containing glass particles containing an acceptor element is applied to the back surface of the p-type semiconductor substrate 10 and subjected to thermal diffusion treatment, whereby a p ⁺ -type diffusion layer is formed on the back surface. (High concentration electric field layer) 14 can be formed.

In FIG. 1 (4), an antireflection film 16 is formed on the n-type diffusion layer 12. The antireflection film 16 is formed by applying a known technique. For example, when the antireflection film 16 is a silicon nitride film, it is formed by a plasma CVD method using a mixed gas of SiH ₄ and NH ₃ as a raw material. At this time, hydrogen diffuses into the crystal, and orbitals that do not contribute to the bonding of silicon atoms, that is, dangling bonds and hydrogen are bonded to inactivate defects (hydrogen passivation).

More specifically, the antireflection film 16 has, for example, a flow rate ratio (NH ₃ / SiH ₄ ) of the mixed gas of 0.05 to 1.0 and a reaction chamber pressure of 13.3 Pa (0.1 Torr) to The film is formed under the conditions of 266.6 Pa (2 Torr), a film forming temperature of 300 ° C. to 550 ° C., and a plasma discharge frequency of 100 kHz or more.

  In FIG. 1 (5), a surface electrode metal paste is printed on the antireflection film 16 on the surface (light receiving surface) by screen printing and dried to form a surface electrode metal paste layer 17. As the metal paste for the surface electrode, for example, metal particles and glass particles as essential components, and a resin binder and other additives as required can be used.

Next, the metal paste layer 19 for the back electrode is also formed on the p ⁺ type diffusion layer 14 on the back surface. As described above, in the present invention, the material and forming method of the back electrode metal paste layer 19 are not particularly limited. For example, the back electrode metal paste layer 19 may be formed by applying and drying a back electrode paste containing a metal such as aluminum, silver, or copper. At this time, a silver paste for forming a silver electrode may be partially provided on the back surface for connection between solar cell elements in the module process.

  In FIG. 1 (6), the metal paste layer 17 for surface electrodes is baked and a solar cell element is completed. When fired in the range of 600 ° C. to 900 ° C. for several seconds to several minutes, the antireflection film 16 that is an insulating film is melted by the glass particles contained in the electrode metal paste on the surface side, and the surface of the p-type semiconductor substrate 10 is also partially When melted, the metal particles (for example, silver particles) in the paste are solidified by forming contact portions with the p-type semiconductor substrate 10. Thereby, the formed surface electrode 18 and the p-type semiconductor substrate 10 are electrically connected. This is called fire-through. Similarly, on the back side, the back electrode metal paste of the back electrode metal paste layer 19 is baked to form the back electrode 20.

As described above, in the method of this embodiment, the method for forming the p ⁺ -type diffusion layer (high concentration electric field layer) 14 on the back surface is not limited to the method by conversion from the n-type diffusion layer to the p-type diffusion layer using aluminum. Therefore, the material used for the back electrode 20 is not limited to Group 13 aluminum, and for example, Ag (silver) or Cu (copper) can be applied. Also, the back electrode 20 can be formed thinner than the conventional one.

  An example of the shape of the surface electrode 18 will be described with reference to FIG. In FIG. 2, 30 indicates a bus bar electrode, and 32 indicates a finger electrode. The surface electrode 18 includes a bus bar electrode 30 and finger electrodes 32 intersecting with the bus bar electrode 30. FIG. 2A is a plan view of a solar cell element in which the surface electrode 18 includes a bus bar electrode 30 and a finger electrode 32 intersecting with the bus bar electrode 30 as viewed from the surface. FIG. 2B is a plan view of FIG. It is a perspective view which expands and shows a part.

  Such a surface electrode 18 can be formed by means such as screen printing of the above-described metal paste, plating of an electrode material, or vapor deposition of an electrode material by electron beam heating in a high vacuum. The surface electrode 18 composed of the bus bar electrode 30 and the finger electrode 32 is generally used as an electrode on the light receiving surface side and is well known, and it is possible to apply known forming means for the bus bar electrode and finger electrode on the light receiving surface side. it can.

In the above description, the solar cell element in which the n-type diffusion layer is formed on the front surface, the p ⁺ -type diffusion layer is formed on the back surface, and the front surface electrode and the back surface electrode are further provided on the respective layers has been described. If a layer formation composition is used, it is also possible to produce a back contact type solar cell element. The back contact type solar cell element has all electrodes provided on the back surface to increase the area of the light receiving surface. That is, in the back contact type solar cell element, it is necessary to form both the n-type diffusion region and the p ⁺ -type diffusion region on the back surface to form a pn junction structure. The n-type diffusion layer forming composition of the present invention can form an n-type diffusion site at a specific site, and can therefore be suitably applied to the production of a back contact type solar cell element.

  The present invention includes the use of the n-type diffusion layer forming composition in the production of an n-type diffusion layer, and the formation of the n-type diffusion layer in the production of a solar cell element including the semiconductor substrate, the n-type diffusion layer, and an electrode. Each use of the composition is also encompassed. As described above, by using the n-type diffusion layer forming composition according to the present embodiment, a sheet resistance of a desired shape can be obtained in a specific region in a short time without forming an unnecessary n-type diffusion layer. An n-type diffusion layer in which variation is suppressed can be obtained, and a solar cell element having such an n-type diffusion layer can be obtained without forming an unnecessary n-type diffusion layer.

  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 reagents.

[Example 1]
The composition in terms of oxide is P ₂ O ₅ : 30 mol%, SiO ₂ : 50 mol%, CaO: 10 mol%, TeO ₂ : 10 mol%, the particle shape is block-like, and the volume average particle diameter 10 g of glass particles having a diameter of 0.89 μm, 5 g of ethyl cellulose, 84 g of terpineol, and 1 g of N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane as a silane compound are mixed using an automatic mortar kneader. Thus, a composition for forming an n-type diffusion layer was prepared.

  The shape of the glass particles was determined by observation using a TM-1000 scanning electron microscope manufactured by Hitachi High-Technologies Corporation. The volume average particle diameter of the glass particles was calculated using a LS 13 320 type laser scattering diffraction particle size distribution analyzer (measurement wavelength: 632 nm) manufactured by Beckman Coulter, Inc.

  The viscosity of the composition for forming an n-type diffusion layer was measured using an E-type viscometer EHD type manufactured by Tokyo Keiki Co., Ltd. under the conditions of a sample amount of 0.4 ml and a rotation speed of 5 times / minute (rpm). , 60 Pa · s.

  Moreover, it was 450 degreeC when the softening point of glass was calculated | required with the differential-heat (DTA) curve using the Shimadzu Corporation DTG-60H type | mold differential heat | fever simultaneous thermogravimetric measuring apparatus.

  Next, the prepared composition for forming an n-type diffusion layer is applied by screen printing to a square p-type silicon substrate surface with a side of 156 mm and a square region with a side of 50 mm, and is applied on a hot plate at 150 ° C. The composition was dried for 5 minutes to form an n-type diffusion layer forming composition layer. Subsequently, it was heat-treated in an electric furnace set at 500 ° C. for 5 minutes, cooled to room temperature, and left in the atmosphere for 3 hours. Next, heat treatment was performed for 10 minutes in another electric furnace for heat diffusion described later set to 700 ° C. Here, the silicon substrate was once taken out from the electric furnace, and the state of the glass particles existing on the silicon substrate was examined by microscopic observation. As a result, the region where the composition layer for forming the n-type diffusion layer on the surface of the silicon substrate was entirely covered with molten glass, and no exposed portion was seen. This state was determined as “good”.

  Subsequently, the silicon substrate was again placed in an electric furnace set at 950 ° C., and diffusion treatment was performed for 10 minutes to diffuse phosphorus into the silicon substrate. After the diffusion treatment, in order to remove the glass layer formed on the silicon substrate, the silicon substrate was immersed in hydrofluoric acid for 5 minutes, washed with running water and dried.

  The sheet resistance in a square region having a side of 50 mm to which the composition for forming an n-type diffusion layer was applied was measured at nine measurement points selected so that the intervals were equal, and the average value was obtained. When all the sheet resistance values at the nine measurement points are within the range of the average value ± 2Ω / □, it is judged as “good”, and at least one of the sheet resistance values at the nine measurement points is the average value ± 2Ω / □. If it was not within the range, it was judged as “insufficient”. Furthermore, a comprehensive judgment was made as ○ (both the glass particle melting state and sheet resistance variation suppression were good) or x (at least one evaluation of the glass particle melting state and sheet resistance variation suppression was not good). .

  As a result, it was confirmed that the average value of the sheet resistance was 15Ω / □, and P (phosphorus) diffused to form an n-type diffusion layer. Furthermore, the sheet resistance values at the nine measurement points were all within the range of the average value ± 2Ω / □, and variations in sheet resistance were sufficiently suppressed. The sheet resistance on the back surface was not measurable above the upper limit of measurement, and it was confirmed that no n-type diffusion layer was formed. The sheet resistance was measured at 25 ° C. by a four-probe method using a Loresta-EP MCP-T360 type low resistivity meter manufactured by Mitsubishi Chemical Corporation.

[Examples 2 to 7 and Comparative Example 1]
An n-type diffusion layer was formed on the silicon substrate in the same manner as in Example 1 except that the composition of the glass particles used in Example 1 (converted to oxide, unit: mol%) was changed to the composition shown in Table 1. The suppression of variation in the molten state of the glass particles and the sheet resistance was evaluated. The evaluation results are summarized in Table 2.

  As shown in the above results, Comparative Example 1 in which the glass particles do not contain the specific element has a lower evaluation of the suppression of variation in the glass particle melting state and the sheet resistance than the Example in which the glass particles do not contain the specific element. It was.

Claims (14)

  An n-type diffusion layer forming composition comprising a donor element, glass particles containing at least one selected from the group consisting of Te, Sn, Zn, V and Bi, and a dispersion medium.   2. The n-type diffusion layer forming composition according to claim 1, wherein at least one selected from the group consisting of Te, Sn, Zn, V, and Bi contains Te. The ratio of at least one selected from the group consisting of TeO ₂ , SnO, ZnO, V ₂ O ₅ and Bi ₂ O _{3 in} terms of oxide is 3 mol% or more of the entire glass particles, The n-type diffused layer formation composition of Claim 1 or Claim 2.   The n-type diffusion layer forming composition according to any one of claims 1 to 3, wherein the glass particles further include at least one selected from the group consisting of Ca and Mg.   The n-type diffusion layer forming composition according to any one of claims 1 to 4, wherein the glass particles further contain Si.   Furthermore, the n type diffused layer formation composition of any one of Claims 1-5 containing a silane compound.   The n-type diffusion layer forming composition according to claim 6, wherein the silane compound includes N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane.   The n-type diffusion layer forming composition according to any one of claims 1 to 7, wherein the glass particles have a volume average particle diameter of 10 µm or less.   The n-type diffused layer formation composition of any one of Claims 1-8 whose content rate of the said glass particle is 1 mass%-30 mass%.   The n-type diffusion layer forming composition according to any one of claims 1 to 9, wherein the dispersion medium contains at least one selected from the group consisting of terpineol and butyl carbitol acetate.   The n-type diffusion layer forming composition according to claim 1, wherein the dispersion medium contains ethyl cellulose.   A step of applying the n-type diffusion layer forming composition according to any one of claims 1 to 11 on a semiconductor substrate, and heat applied to the semiconductor substrate to which the n-type diffusion layer forming composition is applied. And a step of forming an n-type diffusion layer by performing a diffusion treatment, and a method of manufacturing a semiconductor substrate with an n-type diffusion layer.   A step of applying the n-type diffusion layer forming composition according to any one of claims 1 to 11 on a semiconductor substrate, and heat applied to the semiconductor substrate to which the n-type diffusion layer forming composition is applied. A method for manufacturing a solar cell element, comprising: performing a diffusion treatment to form an n-type diffusion layer; and forming an electrode on the n-type diffusion layer.   A solar cell element obtained by the manufacturing method according to claim 13.