JP6582747B2 - Composition for forming n-type diffusion layer, method for producing semiconductor substrate having n-type diffusion layer, and method for producing solar cell - Google Patents

Description

  The present invention relates to a composition for forming an n-type diffusion layer, a method for producing a semiconductor substrate having an n-type diffusion layer, and a method for producing a solar battery cell.

The manufacturing process of the conventional crystalline silicon solar cell will be described.
First, a p-type silicon substrate having a textured structure formed on the light-receiving surface side is prepared so as to promote the light confinement effect, and then a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen is prepared. Then, a process for several tens of minutes is performed at 800 ° C. to 900 ° C. to uniformly form an n-type diffusion layer on the surface of the p-type silicon substrate. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on one side where an n-type diffusion layer is originally required, but also on the side and back surfaces. Therefore, a side etching step for removing the n-type diffusion layer formed on the side surface is necessary. In addition, the n-type diffusion layer formed 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 layer is formed by diffusion of aluminum. ^It was converted into a ⁺ type diffusion layer.

On the other hand, in the semiconductor manufacturing field, an n-type diffusion layer is formed by applying a solution containing a phosphate such as diphosphorus pentoxide (P ₂ O ₅ ) or ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ). A forming method has been proposed (see, for example, Patent Document 1). However, since this method uses a solution, as in the gas phase reaction method using the above mixed gas, phosphorus diffuses to the side surface and the back surface. An n-type diffusion layer is also formed on the back surface.

JP 2002-75894 A

  As described above, when forming the n-type diffusion layer, in the gas phase reaction using phosphorus oxychloride, not only one surface (usually the light-receiving surface) that originally requires the n-type diffusion layer but also the other surface (non-light-receiving surface) An n-type diffusion layer is also formed on the light receiving surface, the back surface) and the side surfaces. Also, in the method of applying thermal diffusion by applying a solution containing diphosphorus pentoxide or phosphate, an n-type diffusion layer is formed in addition to the one side that originally requires an n-type diffusion layer, as in the gas phase reaction method. Will be. Therefore, in order to obtain a semiconductor substrate having a pn junction structure as an element, it is necessary to perform etching on the side surface and convert the n-type diffusion layer to the p-type diffusion layer on the back surface. In general, an aluminum paste which is a Group 13 element is applied to the back surface and fired to convert the n-type diffusion layer into a p-type diffusion layer.

  In addition, when the above phosphate is used, phosphates generally have high hygroscopicity, and the diffusion capacity changes due to moisture absorption in the process of forming the n-type diffusion layer, so that the n-type diffusion layer cannot be formed stably. There is a problem. In addition, since phosphate easily reacts with organic matter, carbide remains as a residue even after the semiconductor substrate is etched, causing deterioration of the characteristics of the solar cell.

  The present invention has been made in view of such circumstances, and prevents a decrease in diffusion capacity due to moisture absorption of the composition for forming an n-type diffusion layer and generation of a residue on a semiconductor substrate, and prevents n-type diffusion at a specific site. Provided are a composition for forming an n-type diffusion layer capable of forming a layer, a method for manufacturing a semiconductor substrate having an n-type diffusion layer using the composition for forming an n-type diffusion layer, and a method for manufacturing a solar cell The task is to do.

Specific means for solving the above problems include the following embodiments.
<1> glass particles containing a donor element and Al (aluminum), and a dispersion medium,
The glass particles, when converting the component oxides, _Al 2 _{O 3} and n-type diffusion layer-forming composition containing 0.01 mass% to 1 mass%.

<2> The composition for forming an n-type diffusion layer 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 when the glass particles represent components as oxides, and Al a _{2 O 3, SiO 2, K} 2 O, Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V 2 O 5, SnO, from ZrO _2, and MoO ₃ The composition for forming an n-type diffusion layer according to <1> or <2>, comprising at least one glass component substance selected from the group consisting of:

<4> A step of applying the composition for forming an n-type diffusion layer according to any one of <1> to <3> to a semiconductor substrate;
Applying a thermal diffusion treatment to the semiconductor substrate provided with the n-type diffusion layer forming composition;
A method of manufacturing a semiconductor substrate having an n-type diffusion layer containing

<5> A method for producing a solar cell, comprising a step of forming an electrode on a semiconductor substrate having an n-type diffusion layer produced by the production method according to <4>.

  According to the present invention, an n-type diffusion layer can be formed at a specific site by preventing a decrease in diffusion ability due to moisture absorption of the composition for forming an n-type diffusion layer and generation of residues on the semiconductor substrate. A composition for forming a diffusion layer, a method for manufacturing a semiconductor substrate having an n-type diffusion layer using the composition for forming an n-type diffusion layer, and a method for manufacturing a solar battery cell can be provided.

It is sectional drawing which shows notionally an example of the manufacturing process of a photovoltaic cell. (A) is the top view which looked at the photovoltaic cell from the light-receiving surface side, (B) is a perspective view which expands and shows a part of (A).

  Hereinafter, an example of embodiments of a composition for forming an n-type diffusion layer to which the present invention is applied, a method for producing a semiconductor substrate having an n-type diffusion layer, and a method for producing a solar battery cell will be described in detail with reference to the drawings. To do. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and the present invention is not limited thereto. Moreover, the magnitude | size of the member in each figure is notional, The relative relationship of the magnitude | size between members is not limited to this.

In this specification, the term “process” includes a process that is independent of other processes and includes the process if the purpose of the process is achieved even if it cannot be clearly distinguished from the other processes. It is.
In the present specification, the numerical ranges indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the present specification, the content of each component in the composition is the sum of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. It means the content rate of.
In the present specification, the particle diameter of each component in the composition is a mixture of the plurality of types of particles present in the composition unless there is a specific indication when there are a plurality of types of particles corresponding to each component in the composition. Means the value of.
In this specification, the term “layer” refers to the case where the layer is formed only in a part of the region in addition to the case where the layer is formed over the entire region. Is also included.

<Composition for forming n-type diffusion layer>
The composition for forming an n-type diffusion layer of the present embodiment contains glass particles containing a donor element and Al (aluminum), and a dispersion medium. When the glass particles convert the components into oxides, Al ₂ O ₃ is contained in an amount of 0.01% by mass to 1% by mass. The composition for forming an n-type diffusion layer may contain other additives as necessary in consideration of impartability, moisture resistance of glass particles, and the like.

  Here, the composition for forming an n-type diffusion layer is a material that contains a donor element and can form an n-type diffusion layer on a semiconductor substrate by thermally diffusing the donor element after being applied to the semiconductor substrate. Say.

By using the composition for forming an n-type diffusion layer of the present embodiment, an n-type diffusion layer is formed only at a desired site, and unnecessary n-type diffusion layers tend not to be formed on the back surface and side surfaces. The reason is not clear, but can be considered as follows.
Since the glass particles in the composition for forming an n-type diffusion layer are “in glass form”, the donor element is sufficiently bonded to the elements in the glass particles or is incorporated into the glass particles. It is presumed that the element becomes difficult to evaporate, and as a result, the occurrence of out diffusion is suppressed during the thermal diffusion treatment.

Therefore, if the composition for forming an n-type diffusion layer according to this embodiment is applied, the side etching step that is essential in the conventional vapor phase reaction method is not required, and the process is simplified. In addition, the step of converting the n-type diffusion layer formed on the back surface into the p ⁺ -type diffusion layer is not necessary. Therefore, the method for forming the p ⁺ -type diffusion layer on the back surface and the material, shape, and thickness of the back electrode are not limited, and these options 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.

  In addition, the glass particle contained in the composition for n type diffused layer formation fuse | melts at the time of a thermal diffusion process, and a glass layer is formed on an n type diffused layer. In the conventional gas phase reaction method and the method of applying a phosphate-containing solution, a glass layer is formed on the n-type diffusion layer, and thus the glass layer generated in this embodiment is the same as the conventional method. Further, it can be removed by etching. Therefore, the n-type diffusion layer forming composition of this embodiment does not generate unnecessary products and does not increase the number of steps as compared with the conventional method.

  Moreover, since glass particles are difficult to volatilize at the time of thermal diffusion treatment, the generation of volatilized gas tends to prevent the formation of n-type diffusion layers not only on the surface but also on the back surface and side surfaces.

Furthermore, glass particles, when converting the component oxides, the _Al 2 _{O 3} containing 0.01 wt% to 1 wt%. When the content of Al ₂ O ₃ when the component is converted to an oxide is 0.01% by mass or more, a change in diffusion capacity due to moisture absorption tends to be prevented. Further, when the content of Al ₂ O ₃ when the component is converted to oxide is 1% by mass or less, Al as an acceptor element diffuses in a high concentration in the semiconductor substrate to form a p-type diffusion layer. You can avoid that.

  Glass particles containing a donor element and Al (aluminum) will be described in detail. In the present specification, the “glass particles” mean glass (amorphous solid exhibiting a glass transition phenomenon) in the form of particles.

  A donor element is an element that can form an n-type diffusion layer by doping into a semiconductor substrate. As the donor element, a Group 15 element can be used, and examples thereof include P (phosphorus), Sb (antimony), As (arsenic), and Bi (bismuth). 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).

Examples of the donor element-containing material used for introducing the donor element into the glass particles include P ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ , Bi ₂ O ₃ , and As ₂ O _3. It is preferable to use at least one selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ , and Sb ₂ O ₃ .

Moreover, the glass particles contain Al (aluminum) in addition to the donor element. Among the donor elements, glass particles containing P ₂ O ₅ or P ₂ O ₃ in terms of oxides generally have an unstable structure and thus have high hygroscopicity, so that phosphorus is dissolved out of the glass particles and thermal diffusion treatment is performed. Sometimes phosphorus scatters. When phosphorus is thus scattered, the amount of phosphorus diffused into the semiconductor substrate is reduced. Further, phosphorus dissolved out of the glass particles may react with an organic substance such as a dispersion medium, and may leave a carbide as a residue on the semiconductor substrate after the thermal diffusion treatment. Al (aluminum) can intervene in an unstable glass skeleton containing P ₂ O ₅ or P ₂ O ₃ in oxide display, and can stabilize the glass skeleton.

  The glass particles can control the melting temperature, softening point, glass transition point, chemical durability, and the like by adjusting the component ratio as necessary. From this point of view, the glass particles preferably contain other elements other than the donor element and Al (aluminum). Examples of other elements include Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, V, Sn, Zr, Mo, La, Nb, Ta, Y, Ti, Ge, Te, and Lu are mentioned.

Examples of glass component substances used for introducing other elements into glass particles include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, and CdO. , V ₂ O ₅ , SnO, ZrO ₂ , MoO ₃ , La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , GeO ₂ , TeO ₂ , and Lu ₂ O _3. Among them, 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 _{3 are used.} It is preferable to use at least one selected from the group.

When the glass particles are expressed as oxides, 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 , Al ₂ O ₃ , , 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 ₃ And at least one glass component substance.
From the viewpoint of moisture resistance, the glass particles have at least one donor element-containing material selected from the group consisting of P ₂ O ₃ and P ₂ O ₅ , Al ₂ O ₃ , _SiO 2, CaO, and it is more preferred to contain, at least one glass component material selected from the group consisting of MgO.

Specific examples of glass particles containing a donor element and Al (aluminum) include, for example, P ₂ O ₅ —SiO ₂ —Al ₂ O ₃ -based glass particles and P ₂ O ₅ —K when the component is expressed as an oxide. _{2 O-Al} 2 _{O 3} based glass _{particles, P 2 O 5 -Na 2 O} -Al 2 O 3 based glass _{particles, P 2 O 5 -Li 2 O} -Al 2 O 3 based glass _particles, P 2 _{O 5} - _BaO-Al 2 _{O 3} based glass _{particles, P 2 O 5 -SrO-Al} 2 O 3 based glass _{particles, P 2 O 5 -CaO-Al} 2 O 3 based glass _{particles, P 2 O 5 -MgO-Al} 2 O ₃ based glass _{particles, P 2 O 5 -BeO-Al} 2 O 3 based glass _{particles, P 2 O 5 -ZnO-Al} 2 O 3 based glass _{particles, P 2 O 5 -CdO-Al} 2 O 3 based glass particles, _{P 2 O 5 -PbO-Al 2} O 3 based glass Scan _{particles, P 2 O 5 -V 2 O} 5 -Al 2 O 3 based glass _{particles, P 2 O 5 -SnO-Al} 2 O 3 based glass _{particles, P 2 O 5 -GeO 2 -Al} 2 O 3 based glass _{particle, P 2 O 5 -Sb 2 O} 3 -Al 2 O 3 based glass _{particles, P 2 O 5 -TeO 2 -Al} 2 O 3 based glass particles, and _{P 2 O 5 -As 2 O 3} -Al 2 O ₃ type | system | group glass particle is mentioned.
In the above has been illustrated glass particles containing 3 ingredients, for _{example, P 2 O 5 -SiO 2 -MgO} -Al 2 O 3 based glass _{particles, P 2 O 5 -SiO 2 -CaO} -Al 2 O 3 based glass particles , And P ₂ O ₅ —SiO ₂ —CaO—MgO—Al ₂ O ₃ -based glass particles, if necessary, may be glass particles containing four or more components.

  The content of the donor element in the glass particles is desirably set as appropriate in consideration of the melting temperature, softening point, glass transition point, and chemical durability of the glass particles. The donor element content in the glass particles is preferably 5% by mass to 95% by mass and more preferably 15% by mass to 60% by mass when converted to oxide. When the content of the donor element is 5% by mass or more, an excessive increase in the softening point of the glass particles is suppressed, and a uniform glass layer tends to be formed during the thermal diffusion treatment. On the other hand, when the content of the donor element is 95% by mass or less, a glass form tends to be easily obtained.

  Further, the content of Al (aluminum) in the glass particles is 0.01% by mass to 1% by mass and preferably 0.1% by mass to 0.5% by mass when converted to oxide. . By making the content of Al (aluminum) 0.01% by mass or more, the effect of stabilizing the glass structure tends to be easily obtained. On the other hand, by setting the Al (aluminum) content to 1% by mass or less, the acceptor element Al diffuses in a high concentration in the semiconductor substrate to form a p-type diffusion layer, which causes a leakage current. Can be avoided.

  The softening point of the glass particles is preferably 200 ° C. to 1000 ° C., and more preferably 500 ° C. to 900 ° C., from the viewpoints of diffusibility and dripping at the time of thermal diffusion treatment.

The average particle size of the glass particles is preferably 10 μm or less. When glass particles having an average particle size of 10 μm or less are used, a smooth coating film tends to be obtained. The average particle size of the glass particles is more preferably 1 μm or less, and further preferably 0.5 μm or less. The lower limit of the average particle size of the glass particles is not particularly limited, and is, for example, 0.01 μm or more.
The average particle size of the glass particles is a value measured by a laser scattering diffraction particle size distribution measuring device or the like, and is a particle size (D50) corresponding to 50% of volume accumulation from the small diameter side in the particle size distribution.

The method for producing the glass particles is not particularly limited. For example, glass particles are 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, quartz, and carbon. 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, stirring is preferably performed so that the melt becomes uniform.
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 apparatus such as a jet mill, a bead mill, or a ball mill can be applied to the pulverization.

  The content rate of the glass particles in the composition for forming an n-type diffusion layer is determined in consideration of the imparting property, the diffusibility of the donor element, and the like. Generally, the content of the glass particles in the composition for forming an n-type diffusion layer is preferably 5% by mass to 95% by mass, and more preferably 10% by mass to 50% by mass.

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. Specifically, a binder, a solvent, or the like is employed as the dispersion medium.

Examples of the binder include dimethylaminoethyl (meth) acrylate polymer, polyvinyl alcohol, polyacrylamide compound, polyvinylamide compound, polyvinylpyrrolidone, poly (meth) acrylic acid compound, polyethylene oxide compound, polysulfonic acid, acrylamide alkylsulfonic acid, and cellulose. Ether compound, cellulose derivative, carboxymethylcellulose, hydroxyethylcellulose, ethylcellulose, gelatin, starch, starch derivative, sodium alginate, xanthan, guar gum, guar gum derivative, scleroglucan, tragacanth, dextrin derivative, acrylic acid resin, acrylic ester resin, Select butadiene resin, styrene resin, their copolymers, and silicon dioxide as appropriate. That. These binders may be used alone or in combination of two or more.
“(Meth) acrylate” means acrylate or methacrylate, and “(meth) acrylic acid” means acrylic acid or methacrylic acid.

  The molecular weight of the binder is not particularly limited, and is preferably adjusted as appropriate in consideration of the desired viscosity of the n-type diffusion layer forming composition.

  Solvents 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, dipropyl ketone, Ketone solvents such as diisobutylketone, 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, ethylene glycol Diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl 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- Chill ether, triethylene glycol methyl-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, tetraethylene glycol di-n-butyl ether, tetraethylene Glycol methyl-n-hexyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol di-n-butyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl Ether, dipropylene glycol Ru-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 glycol Ether solvents such as alkyl di-n-butyl ether and tetrapropylene glycol methyl-n-hexyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, n-acetate Pentyl, sec-pentyl acetate, 3-methoxybutyl acetate, methyl pentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, nonyl acetate , Methyl acetoacetate, ethyl acetoacetate, glycol diacetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, Lactic acid n- Ester solvents such as mill; 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-n-butyl ether acetate , Ether ester solvents such as 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, triethylene glycol methyl ether acetate; Tolyl, N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N- Aprotic polar solvents such as dimethyl sulfoxide; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, n-pentanol, isopentanol, 2-methylbutanol, sec -Pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhe Xanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, Alcohol solvents such as 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol and tripropylene glycol; phenol solvents such as phenol; terpinene, terpineol, myrcene, alloocimene, limonene, dipentene , Terpene solvents such as pinene, carvone, ocimene and ferrandrene; ethylene glycol monomethyl ether, ethylene glycol Cole 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 Examples include glycol monoether solvents such as glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and tripropylene glycol monomethyl ether; water. These solvents may be used alone or in combination of two or more.

The content of the dispersion medium in the composition for forming an n-type diffusion layer is determined in consideration of the imparting property and the donor concentration.
The viscosity of the composition for forming an n-type diffusion layer is preferably 10 mPa · s to 500,000 mPa · s, more preferably 1000 mPa · s to 50000 mPa · s in consideration of applicability.

The composition for forming an n-type diffusion layer may further contain other additives as necessary. Among other additives, those that improve the imparting property include, for example, organic fillers, inorganic fillers, thixotropic imparting agents such as organic acid salts, wettability improvers, leveling agents, surfactants, plasticizers, and fillers. Agents, antifoaming agents, stabilizers, antioxidants, and perfumes. Examples of other additives that improve the moisture resistance of glass particles include silane coupling agents, metal alkoxides, silicone resins, and alkylsilazane compounds. Each of these additives can be used in the composition for forming an n-type diffusion layer in an amount of about 0.01% by mass to 20% by mass. These additives may be used alone or in combination of two or more.
Among these additives, silane coupling is based on the fact that moisture interacts with the surface of the glass particles and that the functional groups oriented on the surface of the glass particles are hydrophobic and can bind to the binder. An agent is preferred, and a silane coupling agent having an amino group is more preferred.

  The composition for forming an n-type diffusion layer differs from the composition for forming an electrode in terms of the content of metal particles. The content rate of the metal particles in the composition for forming an n-type diffusion layer is, for example, 1 mass ppm or less, and preferably 0.01 mass ppm or less.

<The manufacturing method of a semiconductor substrate which has an n type diffused layer, and the manufacturing method of a photovoltaic cell>
The method for manufacturing a semiconductor substrate having an n-type diffusion layer according to this embodiment includes a step of applying the above-described composition for forming an n-type diffusion layer to a semiconductor substrate, and a semiconductor substrate provided with the composition for forming an n-type diffusion layer. Applying a thermal diffusion treatment.

  The manufacturing method of the photovoltaic cell of this embodiment includes the process of forming an electrode in the semiconductor substrate which has an n-type diffusion layer manufactured by the manufacturing method of the semiconductor substrate which has the n-type diffusion layer mentioned above.

  The semiconductor substrate is not particularly limited, and a semiconductor substrate used for a solar battery cell 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 include a substrate, an indium phosphide substrate, a silicon carbide substrate, a germanium silicide substrate, and a copper indium selenium substrate. Examples of the silicon substrate include a crystalline silicon substrate. Among these semiconductor substrates, it is preferable to use a silicon substrate.

Hereinafter, although the manufacturing method of the semiconductor substrate which has an n type diffused layer, and the manufacturing method of a photovoltaic cell are demonstrated, referring FIG. 1, this invention is not limited to this. FIG. 1 is a schematic cross-sectional view conceptually showing an example of a manufacturing process of a solar battery cell. In the subsequent drawings, common constituent elements are denoted by the same reference numerals.
In addition, although FIG. 1 demonstrates the case where a p-type crystalline silicon substrate is used, you may use an n-type crystalline silicon substrate. The crystalline silicon substrate may be an amorphous silicon substrate or a substrate made of other than silicon.

  In FIG. 1A, an alkaline solution is applied to the p-type crystalline silicon substrate 10 to remove the damaged layer, and a texture structure is obtained by etching. Specifically, the damaged layer on the silicon surface 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 (the description of the texture structure is omitted in the figure). In the solar battery cell, by forming a texture structure on the light receiving surface (front surface) side, a light confinement effect is promoted and high efficiency is achieved.

  In FIG. 1 (2), the n-type diffusion layer forming composition layer 11 is formed by applying the n-type diffusion layer forming composition described above to the surface of the p-type crystalline silicon substrate 10, that is, the light receiving surface. To do. There is no restriction | limiting in the application | coating method of the composition for n-type diffused layer formation, For example, a printing method, a spin coat method, brush coating, a spray method, a doctor blade method, a roll coat method, and an inkjet method is mentioned.

  Depending on the composition of the n-type diffusion layer forming composition, a drying step for volatilizing the solvent contained in the composition may be necessary after application. In this case, for example, drying is performed at a temperature of about 80 ° C. to 300 ° C. for about 1 minute to 10 minutes when using a hot plate, and about 10 minutes to 30 minutes when using a dryer or the like. The drying conditions depend on the solvent composition of the n-type diffusion layer forming composition and are not particularly limited to the above conditions.

When the manufacturing method of this embodiment is used, the manufacturing method of the high-concentration electric field layer (p ⁺ -type diffusion layer) 14 on the back surface is a method based on conversion from an n-type diffusion layer to a p-type diffusion layer using aluminum. Any method can be adopted without limitation, and the choice of manufacturing method is expanded. Therefore, for example, the layer 13 can be formed by applying a composition containing a Group 13 element such as B (boron), and the high concentration electric field layer 14 can be formed.

In FIG. 1 (3), the p-type crystalline silicon substrate 10 on which the n-type diffusion layer forming composition layer 11 is formed is subjected to a thermal diffusion treatment at 600 ° C. to 1200 ° C. By this thermal diffusion treatment, the donor element is diffused into the p-type crystalline silicon substrate 10 and the n-type diffusion layer 12 is formed. A known continuous furnace, batch furnace, or the like can be applied to the thermal diffusion treatment.
Since a glass layer (not shown) such as phosphate glass is formed on the surface of the n-type diffusion layer 12, this glass layer is removed by etching. As the etching, 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.

  In the method of forming the n-type diffusion layer 12 using the composition for forming an n-type diffusion layer of the present embodiment shown in FIGS. 1 (2) and (3), the glass particles are exposed to the atmosphere after the drying step. However, even if moisture in the atmosphere is adsorbed, phosphorus hardly disappears from the glass particles, so that it is less affected by the surrounding environment (humidity) and stable diffusion is possible. Further, since phosphorus in the glass particles hardly reacts with the binder, generation of a residue on the surface of the p-type crystalline silicon substrate after the etching process is suppressed.

Further, in the method of forming the n-type diffusion layer 12 using the composition for forming an n-type diffusion layer of the present embodiment, the n-type diffusion layer 12 is formed only at a desired portion, and unnecessary n-type is formed on the back surface and the side surface. Formation of the diffusion layer is suppressed.
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 this manufacturing method, the side etching process becomes unnecessary, and the process is simplified.

Further, in the conventional manufacturing method, it is necessary to convert the n-type diffusion layer formed on the back surface into the p-type diffusion layer. As this conversion method, a paste of aluminum which is a Group 13 element is applied to the n-type diffusion layer on the back surface, and heat diffusion treatment is performed, and aluminum is diffused into the n-type diffusion layer to convert it into a p-type diffusion layer. The method to do is adopted. In this method, in order to sufficiently convert to the p-type diffusion layer and to form a high concentration electric field layer of p ⁺ layer, an aluminum amount of a certain amount or more is required. Therefore, the aluminum layer is formed thick. There was a need. 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 thermal diffusion treatment and cooling, which causes warpage of the silicon substrate. It was.
This internal stress has a problem in that the crystal grain boundary of the crystalline silicon is damaged and the power loss increases. In addition, the warpage of the silicon substrate easily causes the cell to be damaged when the solar battery cell is transported in the module process and when it is connected to a copper wire called a tab wire. In recent years, due to the improvement of slicing technology, the thickness of the crystalline silicon substrate is being reduced, and the cells tend to be easily broken.

  On the other hand, according to the manufacturing method of the present embodiment, since an unnecessary n-type diffusion layer is hardly formed on the back surface, there is no need to perform conversion from the n-type diffusion layer to the p-type diffusion layer. The necessity of thickening is lost. As a result, generation of internal stress in the silicon substrate and warpage of the silicon substrate can be suppressed. As a result, it is possible to suppress an increase in power loss of the solar battery cell and damage to the cell.

When the manufacturing method of this embodiment is used, the manufacturing method of the high-concentration electric field layer (p ⁺ -type diffusion layer) 14 on the back surface is a method based on conversion from an n-type diffusion layer to a p-type diffusion layer using aluminum. Any method can be adopted without limitation, and the choice of manufacturing method is expanded.
Further, as will be described later, the material used for the back electrode paste layer 20 is not limited to Group 13 aluminum, and for example, Ag (silver) and Cu (copper) can be applied. It is possible to form a thinner thickness than the conventional one.

In FIG. 1 (4), the antireflection layer 16 is formed on the n-type diffusion layer 12. The antireflection layer 16 is formed by applying a known technique. For example, when the antireflection layer 16 is a silicon nitride layer, it can be formed by a plasma CVD (Chemical Vapor Deposition) 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 mixed gas flow rate ratio NH ₃ / SiH ₄ is 0.05 to 1.0, the reaction chamber pressure is 13.3 Pa to 266.6 Pa (0.1 Torr to 2 Torr), and the temperature at the time of layer formation The silicon nitride layer can be formed under conditions of 300 ° C. to 550 ° C. and a frequency for plasma discharge of 100 kHz or more.

  In FIG. 1 (5), a light receiving surface electrode metal paste is printed on the antireflection layer 16 on the surface (light receiving surface) by a screen printing method and dried to form a light receiving surface electrode paste layer 18. The metal paste for the light-receiving surface electrode includes metal particles and glass particles as essential components, and includes a resin binder, other additives, and the like as necessary.

  Next, the back electrode paste layer 20 is also formed on the high-concentration electric field layer 14 on the back surface. As described above, in the present embodiment, the material and forming method of the back electrode paste layer 20 are not particularly limited. For example, the back electrode paste layer 20 may be formed by applying a metal paste for the back electrode including a metal such as aluminum, silver, or copper and drying the paste. At this time, a silver paste for forming a silver electrode may be partially provided on the back surface for connection between cells in the module process.

  In FIG. 1 (6), the light-receiving surface electrode paste layer 18 and the back electrode paste layer 20 are heat-treated (fired) to form the light-receiving surface electrode 19 and the back electrode 21, respectively, thereby completing the solar battery cell. When heat treatment (baking) is performed in the range of 600 ° C. to 900 ° C. for several seconds to several minutes, the antireflection layer 16 that is an insulating layer is melted by the glass particles contained in the metal paste for the light receiving surface electrode on the light receiving surface side, and further p-type A part of the surface of the crystalline silicon substrate 10 is also melted, and metal particles (for example, silver particles) in the paste form a contact portion with the p-type crystalline silicon substrate 10 to solidify. Thereby, the formed light-receiving surface electrode 19 and the p-type crystalline silicon substrate 10 are electrically connected. This is called fire-through.

  The shape of the light receiving surface electrode 19 will be described. The light receiving surface electrode 19 includes a bus bar electrode 30 and a finger electrode 32 intersecting with the bus bar electrode 30. FIG. 2 (A) is a plan view of a photovoltaic cell in which the light-receiving surface electrode 19 is composed of a bus bar electrode 30 and finger electrodes 32 intersecting with the bus bar electrode 30, as viewed from the light-receiving surface side. FIG. 2B is an enlarged perspective view showing a part of FIG.

  Such a light-receiving surface electrode 19 can be formed by means such as screen printing of the above-described metal paste, plating of the electrode material, or vapor deposition of the electrode material by electron beam heating in a high vacuum. The light receiving surface electrode 19 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 can be formed by a known method.

In the above description, the solar cell in which the n-type diffusion layer is formed on the light-receiving surface, the p ⁺ -type diffusion layer is formed on the back surface, and the light-receiving surface electrode and the back electrode are further provided on the respective layers has been described. If the composition for n type diffused layer formation is used, it is also possible to manufacture a back contact type photovoltaic cell.
The back contact type solar battery cell 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, it is necessary to form both the n-type diffusion site and the p ⁺ -type diffusion site on the back surface to form a pn junction structure. The composition for forming an n-type diffusion layer of the present embodiment can form an n-type diffusion site only in a specific site, and therefore can be suitably applied to the production of a back contact type solar battery cell. .

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

[Example 1]
P ₂ O ₅ —SiO ₂ —MgO—Al ₂ O ₃ glass particles (in terms of oxide, P ₂ O ₅ : 59.0%, SiO ₂ : 28.6%, MgO: 12.0%, Al ₂ 20 g of O ₃ : 0.4%), 5 g of ethyl cellulose (Ethocel STD10, manufactured by Dow Chemical) and 75 g of terpineol (Turpineol LW, manufactured by Nippon Terpene Chemical Co., Ltd.) are mixed to form a paste, thereby forming an n-type diffusion layer A composition was prepared.

  Next, the prepared composition for forming an n-type diffusion layer was applied to the surface of a p-type silicon substrate in the shape of a square (50 mm × 50 mm) by screen printing and dried on a hot plate at 150 ° C. for 3 minutes. Within 30 minutes after drying, thermal diffusion treatment was performed for 15 minutes in an electric furnace set at 950 ° C. After the thermal diffusion treatment, the p-type silicon substrate was immersed in 5% hydrofluoric acid for 5 minutes in order to remove the glass layer formed on the surface of the p-type silicon substrate. Thereafter, the p-type silicon substrate was washed with running water and naturally dried.

The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 12 Ω / cm ² , and it was confirmed that P (phosphorus) diffused to form an n-type diffusion layer. It was. The sheet resistance on the back surface was 1000000 Ω / cm ² or more and could not be measured, and it was confirmed that no n-type diffusion layer was formed. Moreover, it was confirmed that there is no etching residue in the formation region of the n-type diffusion layer.

Next, after forming an n-type diffusion layer by the same method as described above, the out diffusion was evaluated by secondary ion mass spectrometry (SIMS). On the surface of the p-type silicon substrate to which the composition for forming an n-type diffusion layer was applied, the concentration of P (phosphorus) was 10 ²¹ atoms / cm ³ . On the other hand, at a point 2 mm away from the end of the portion to which the n-type diffusion layer forming composition is applied, the concentration of P (phosphorus) is 10 ¹⁷ atoms / cm ³ , and the n-type diffusion layer forming composition is It was 1 / 10,000 of the concentration of P (phosphorus) in the applied portion. Thereby, it was confirmed that out diffusion was suppressed. Further, on the surface of the p-type silicon substrate where the n-type diffusion layer forming composition is applied, the concentration of Al (aluminum) is 10 ¹⁶ atoms / cm ³ , and Al (aluminum) is hardly diffused. confirmed.

Next, in order to evaluate the change in diffusion capacity due to moisture absorption, the composition for forming an n-type diffusion layer was applied to the surface of a p-type silicon substrate, dried on a hot plate at 150 ° C. for 3 minutes, and then at a temperature of 25 ° C. And left under high humidity of 60% RH for 12 hours. And the thermal diffusion process was performed for 15 minutes with the electric furnace set to 950 degreeC. After the thermal diffusion treatment, the glass layer formed on the surface of the p-type silicon substrate was removed by immersing in 5% hydrofluoric acid for 5 minutes. Thereafter, the p-type silicon substrate was washed with running water and naturally dried. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 12 Ω / cm ² , and P (phosphorus) diffusion did not change. It was also confirmed that there was no etching residue on the p-type silicon substrate.

[Example 2]
Instead of the glass particles used in Example 1, P ₂ O ₅ —SiO ₂ —MgO—Al ₂ O ₃ glass particles (in terms of oxide, P ₂ O ₅ : 59.3%, SiO ₂ : 28.64). %, MgO: 12.0%, Al ₂ O ₃ : 0.06%) was used in the same manner as in Example 1 to prepare an n-type diffusion layer forming composition.

Next, an n-type diffusion layer was formed in the same manner as in Example 1 using the prepared composition for forming an n-type diffusion layer. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 12 Ω / cm ² , and it was confirmed that P (phosphorus) diffused to form an n-type diffusion layer. It was. The sheet resistance on the back surface was 1000000 Ω / cm ² or more and could not be measured, and it was confirmed that no n-type diffusion layer was formed. Moreover, it was confirmed that there is no etching residue in the formation region of the n-type diffusion layer.

Next, outdiffusion was evaluated by secondary ion mass spectrometry (SIMS) in the same manner as in Example 1. On the surface of the p-type silicon substrate to which the composition for forming an n-type diffusion layer was applied, the concentration of P (phosphorus) was 10 ²¹ atoms / cm ³ . On the other hand, at a point 2 mm away from the end of the portion to which the n-type diffusion layer forming composition is applied, the concentration of P (phosphorus) is 10 ¹⁷ atoms / cm ³ , and the n-type diffusion layer forming composition is It was 1 / 10,000 of the concentration of P (phosphorus) in the applied portion. Thereby, it was confirmed that out diffusion was suppressed. Further, on the surface of the p-type silicon substrate where the n-type diffusion layer forming composition is applied, the concentration of Al (aluminum) is 10 ¹⁶ atoms / cm ³ , and Al (aluminum) is hardly diffused. confirmed.

Next, the change in the diffusion capacity due to moisture absorption was evaluated in the same manner as in Example 1. The sheet resistance of the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 13 Ω / cm ² , and P (phosphorus) diffusion hardly changed. It was also confirmed that there was no etching residue on the p-type silicon substrate.

[Example 3]
Instead of the glass particles used in Example 1, P ₂ O ₅ —SiO ₂ —MgO—Al ₂ O ₃ glass particles (in terms of oxide, P ₂ O ₅ : 59.0%, SiO ₂ : 28.5) %, MgO: 11.6%, Al ₂ O ₃ : 0.9%) was used in the same manner as in Example 1 to prepare an n-type diffusion layer forming composition.

Next, an n-type diffusion layer was formed in the same manner as in Example 1 using the prepared composition for forming an n-type diffusion layer. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 14 Ω / cm ² , and it was confirmed that P (phosphorus) diffused to form an n-type diffusion layer. It was. The sheet resistance on the back surface was 1000000 Ω / cm ² or more and could not be measured, and it was confirmed that no n-type diffusion layer was formed. It was also confirmed that there was no etching residue in the n-type diffusion layer formation region.

Next, outdiffusion was evaluated by secondary ion mass spectrometry (SIMS) in the same manner as in Example 1. On the surface of the p-type silicon substrate to which the composition for forming an n-type diffusion layer was applied, the concentration of P (phosphorus) was 10 ²¹ atoms / cm ³ . On the other hand, the P (phosphorus) concentration is 10 ¹⁶ atoms / cm ³ at a point 2 mm away from the end of the portion to which the n-type diffusion layer forming composition is applied, and the n-type diffusion layer forming composition is It was 1/100000 of the density | concentration of P (phosphorus) of the provided part. Thereby, it was confirmed that out diffusion was suppressed. Further, the Al (aluminum) concentration is 5 × 10 ¹⁶ atoms / cm ³ on the surface of the portion of the p-type silicon substrate to which the composition for forming the n-type diffusion layer is applied, and Al (aluminum) is hardly diffused. It was confirmed.

Next, the change in the diffusion capacity due to moisture absorption was evaluated in the same manner as in Example 1. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 14 Ω / cm ² , and P (phosphorus) diffusion did not change. It was also confirmed that there was no etching residue on the p-type silicon substrate.

[Example 4]
Example 1 except that 2 g of N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane (KBM602, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the composition for forming an n-type diffusion layer of Example 1. Similarly, an n-type diffusion layer forming composition was prepared.

Next, an n-type diffusion layer was formed in the same manner as in Example 1 using the prepared composition for forming an n-type diffusion layer. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 12 Ω / cm ² , and it was confirmed that P (phosphorus) diffused to form an n-type diffusion layer. It was. The sheet resistance on the back surface was 1000000 Ω / cm ² or more and could not be measured, and it was confirmed that no n-type diffusion layer was formed. It was also confirmed that there was no etching residue in the n-type diffusion layer formation region.

Next, outdiffusion was evaluated by secondary ion mass spectrometry (SIMS) in the same manner as in Example 1. On the surface of the p-type silicon substrate to which the composition for forming an n-type diffusion layer was applied, the concentration of P (phosphorus) was 10 ²¹ atoms / cm ³ . On the other hand, at a point 2 mm away from the end of the portion to which the n-type diffusion layer forming composition is applied, the concentration of P (phosphorus) is 10 ¹⁷ atoms / cm ³ , and the n-type diffusion layer forming composition is It was 1 / 10,000 of the concentration of P (phosphorus) in the applied portion. Thereby, it was confirmed that out diffusion was suppressed. Further, on the surface of the p-type silicon substrate where the n-type diffusion layer forming composition is applied, the concentration of Al (aluminum) is 10 ¹⁶ atoms / cm ³ , and Al (aluminum) is hardly diffused. confirmed.

Next, the change in the diffusion capacity due to moisture absorption was evaluated in the same manner as in Example 1. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 12 Ω / cm ² , and P (phosphorus) diffusion did not change. It was also confirmed that there was no etching residue on the p-type silicon substrate.

[Comparative Example 1]
Instead of the glass particles used in Example 1, P ₂ O ₅ —SiO ₂ —MgO-based glass particles (in terms of oxide, P ₂ O ₅ : 59.3%, SiO ₂ : 28.7%, MgO: 12 0.0%) was used in the same manner as in Example 1 to prepare an n-type diffusion layer forming composition.

Next, an n-type diffusion layer was formed in the same manner as in Example 1 using the prepared composition for forming an n-type diffusion layer. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 12 Ω / cm ² , and it was confirmed that P (phosphorus) diffused to form an n-type diffusion layer. It was. The sheet resistance on the back surface was 500 Ω / cm ² , and it was confirmed that the n-type diffusion layer was slightly formed. It was also confirmed that there was no etching residue in the n-type diffusion layer formation region.

Next, outdiffusion was evaluated by secondary ion mass spectrometry (SIMS) in the same manner as in Example 1. On the surface of the p-type silicon substrate to which the composition for forming an n-type diffusion layer was applied, the concentration of P (phosphorus) was 10 ²¹ atoms / cm ³ . On the other hand, at a point 2 mm away from the end of the portion to which the composition for forming an n-type diffusion layer was applied, the concentration of P (phosphorus) was 10 ¹⁹ atoms / cm ³ , and out-diffusion was confirmed.

Next, the change in the diffusion capacity due to moisture absorption was evaluated in the same manner as in Example 1. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 25 Ω / cm ² , and the diffusion of P (phosphorus) was changed. Moreover, an etching residue was confirmed on the p-type silicon substrate.

[Comparative Example 2]
Instead of the glass particles used in Example 1, P ₂ O ₅ —SiO ₂ —MgO—Al ₂ O ₃ glass particles (in terms of oxide, P ₂ O ₅ : 59.3%, SiO ₂ : 28.69). %, MgO: 12.0%, Al ₂ O ₃ : 0.006%) was used in the same manner as in Example 1 to prepare an n-type diffusion layer forming composition.

Next, an n-type diffusion layer was formed in the same manner as in Example 1 using the prepared composition for forming an n-type diffusion layer. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 12 Ω / cm ² , and it was confirmed that P (phosphorus) diffused to form an n-type diffusion layer. It was. The sheet resistance on the back surface was 200 Ω / cm ² , and it was confirmed that the n-type diffusion layer was slightly formed. It was also confirmed that there was no etching residue in the n-type diffusion layer formation region.

Next, outdiffusion was evaluated by secondary ion mass spectrometry (SIMS) in the same manner as in Example 1. On the surface of the p-type silicon substrate to which the composition for forming an n-type diffusion layer was applied, the concentration of P (phosphorus) was 10 ²¹ atoms / cm ³ . On the other hand, the P (phosphorus) concentration was 10 ²⁰ atoms / cm ³ at the point 2 mm away from the end of the portion to which the composition for forming an n-type diffusion layer was applied, and out-diffusion was confirmed. Further, on the surface of the p-type silicon substrate where the n-type diffusion layer forming composition is applied, the concentration of Al (aluminum) is 10 ¹⁶ atoms / cm ³ , and Al (aluminum) is hardly diffused. confirmed.

Next, the change in the diffusion capacity due to moisture absorption was evaluated in the same manner as in Example 1. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 25 Ω / cm ² , and the diffusion of P (phosphorus) was changed. Moreover, an etching residue was confirmed on the p-type silicon substrate.

[Comparative Example 3]
Instead of the glass particles used in Example 1, P ₂ O ₅ —SiO ₂ —MgO—Al ₂ O ₃ glass particles (in terms of oxide, P ₂ O ₅ : 58.6%, SiO ₂ : 28.4) %, MgO: 11.2%, Al ₂ O ₃ : 1.8%) was used in the same manner as in Example 1 to prepare an n-type diffusion layer forming composition.

Next, an n-type diffusion layer was formed in the same manner as in Example 1 using the prepared composition for forming an n-type diffusion layer. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 25 Ω / cm ² , and it was confirmed that P (phosphorus) was diffused to form an n-type diffusion layer. However, the value was higher than that of Example 1. This is presumed to be because Al (aluminum) diffused into the p-type silicon substrate. The sheet resistance on the back surface was 1000000 Ω / cm ² or more and could not be measured, and it was confirmed that no n-type diffusion layer was formed. It was also confirmed that there was no etching residue in the n-type diffusion layer formation region.

Next, outdiffusion was evaluated by secondary ion mass spectrometry (SIMS) in the same manner as in Example 1. On the surface of the p-type silicon substrate to which the composition for forming an n-type diffusion layer was applied, the concentration of P (phosphorus) was 10 ²¹ atoms / cm ³ . On the other hand, at a point 2 mm away from the end of the portion to which the n-type diffusion layer forming composition is applied, the concentration of P (phosphorus) is 10 ¹⁷ atoms / cm ³ , and the n-type diffusion layer forming composition is It was 1 / 10,000 of the concentration of P (phosphorus) in the applied portion. Thereby, it was confirmed that out diffusion was suppressed. However, on the surface of the p-type silicon substrate to which the composition for forming an n-type diffusion layer is applied, the Al (aluminum) concentration is 10 ¹⁸ atoms / cm ³ , and Al (aluminum) diffuses at a relatively high concentration. It was confirmed that

Next, the change in the diffusion capacity due to moisture absorption was evaluated in the same manner as in Example 1. The sheet resistance on the surface of the p-type silicon substrate on the side to which the composition for forming an n-type diffusion layer was applied was 25 Ω / cm ² , and the diffusion of P (phosphorus) was not changed. It was also confirmed that there was no etching residue on the p-type silicon substrate.

10 p-type crystalline silicon substrate 12 n-type diffusion layer 14 high-concentration electric field layer 16 antireflection layer 18 light-receiving surface electrode paste layer 19 light-receiving surface electrode 20 back electrode paste layer 21 back electrode 30 bus bar electrode 32 finger electrode

Claims (3)

Containing glass particles containing a donor element and Al (aluminum), and a dispersion medium,
When the glass particles contain 0.01% by mass to 1% by mass of Al ₂ O ₃ when the component is converted to oxide, and P ₂ O ₅ —SiO ₂ —MgO—Al ₂ represents the component as an oxide. A composition for forming an n-type diffusion layer represented by O ₃ . Applying the n-type diffusion layer forming composition according to claim 1 to a semiconductor substrate;
Applying a thermal diffusion treatment to the semiconductor substrate provided with the n-type diffusion layer forming composition;
A method of manufacturing a semiconductor substrate having an n-type diffusion layer containing The manufacturing method of a photovoltaic cell including the process of forming an electrode in the semiconductor substrate which has an n-type diffused layer manufactured by the manufacturing method of Claim 2 .