WO2016068315A1 - Composition for forming n-type diffusion layer, method for producing n-type diffusion layer, and method for manufacturing solar cell element - Google Patents

Abstract

Provided are: a composition for forming an n-type diffusion layer, the composition containing glass powder including a donor element and having a particle diameter d90 of 0.1-1.5 µm, and a dispersion medium; a method for producing an n-type diffusion layer by using the composition; and a method for manufacturing a solar cell element.

Description

N-type diffusion layer forming composition, method for producing n-type diffusion layer, and method for producing solar cell element

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

A manufacturing process of a conventional silicon solar cell element using, for example, a p-type silicon substrate as the semiconductor substrate will be described.
First, a p-type silicon substrate having a texture structure formed on the light receiving surface is prepared so as to promote the light confinement effect and increase the efficiency. This p-type silicon substrate is uniformly n-type 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, nitrogen and oxygen. A diffusion layer is formed. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the surface of the p-type silicon substrate, but also on the side and back surfaces. 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, in the semiconductor manufacturing field, as described in JP-A-2002-75894, a solution containing a phosphate such as ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) as a donor element-containing compound A method for forming an n-type diffusion layer by coating is proposed.
In addition, as described in Japanese Patent No. 4073968, a technique is also known in which a paste containing phosphorus as a donor element is applied as a diffusion source on the surface of a silicon substrate and thermally diffused to form a diffusion layer.

However, in the method described in Japanese Patent Application Laid-Open No. 2002-75894 or Japanese Patent No. 4073968, a donor element or a compound containing the donor element is scattered from a solution or paste as a diffusion source. Similarly to the above, when the diffusion layer is formed, phosphorus may also diffuse into the side surface and the back surface of the p-type silicon substrate. As a result, an n-type diffusion layer may be formed in addition to the applied part.

As described above, when forming the n-type diffusion layer, the vapor phase reaction method using phosphorus oxychloride is applicable only to one side (usually the light-receiving surface or the surface) of the p-type silicon substrate which originally requires the n-type diffusion layer. In addition, an n-type diffusion layer is also formed on the other surface (non-light-receiving surface or back surface) and side surface. In addition, even when a solution or paste containing a phosphorus-containing compound is applied to a p-type silicon substrate and thermally diffused, an n-type diffusion layer is formed on the surface other than the surface of the p-type silicon substrate as in the gas phase reaction method. End up. Therefore, in order for the p-type silicon substrate to have a pn junction structure as a solar cell 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 an element belonging to Group 13 is applied to the back surface of a p-type silicon substrate and baked to convert the n-type diffusion layer into a p + -type diffusion layer. Furthermore, in a method of forming a n-type diffusion layer by applying a conventionally known paste containing a donor element such as phosphorus to a p-type silicon substrate as a diffusion source, the compound containing the donor element is volatilized and gasified to form a donor element. Since the donor element is diffused in a region other than the region where the diffusion is required, it is difficult to selectively form a diffusion layer in a specific region.

In addition, when a coating agent containing a phosphorus compound is used, there may be uneven concentration of diffused phosphorus on the micro scale in the plane of the n-type diffusion layer. In particular, when the coating amount of a coating agent containing a phosphorus compound is reduced, in the drying step of the coating agent containing a phosphorus compound, the solvent rapidly evaporates from the end of the coating region, and the cross-section of the coating region becomes concave. (Coffee ring phenomenon) may occur. Therefore, in the central part of the coating region, when the phosphorus compound abundance ratio is reduced and diffusion occurs in a state where the phosphorus compound abundance ratio is reduced, the phosphorus concentration differs on a microscale in the surface direction or thickness direction of the p-type silicon substrate. A non-uniform n-type diffusion layer may be formed. The presence of a non-uniform n-type diffusion layer leads to a decrease in conversion efficiency of the entire solar cell.

The present invention has been made in view of the above-described conventional problems, and is applicable to a solar cell element using a semiconductor substrate, and can be applied to a specific region without forming an n-type diffusion layer in an unnecessary region. It is an object of the present invention to provide an n-type diffusion layer forming composition capable of forming a uniform n-type diffusion layer, an n-type diffusion layer manufacturing method using the same, and a solar cell element manufacturing method.

The concrete means for achieving the above-mentioned problems are as follows.

<1> An n-type diffusion layer forming composition comprising a glass powder containing a donor element and having a particle diameter d90 of 0.1 μm to 1.5 μm and a dispersion medium.

<2> The n-type diffusion layer forming composition according to <1>, wherein the glass powder has an average particle diameter d50 of 0.05 μm to 0.5 μm.

<3> The n-type diffusion layer forming composition according to <1> or <2>, wherein the donor element is at least one selected from P (phosphorus) and Sb (antimony).

<4> The glass powder includes at least one donor element-containing material selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ , SiO ₂ , K ₂ O, Na ₂ O, Containing at least one glass component material selected from the group consisting of Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO _2, and MoO _3. The n-type diffusion layer forming composition according to any one of <3>.

<5> a step of applying the n-type diffusion layer forming composition according to any one of <1> to <4> on a semiconductor substrate;
Applying a thermal diffusion treatment to the semiconductor substrate after the application of the n-type diffusion layer forming composition;
The manufacturing method of the n type diffused layer which has this.

<6> a step of applying the n-type diffusion layer forming composition according to any one of <1> to <4> on a semiconductor substrate;
Applying a thermal diffusion treatment to the semiconductor substrate after application of the n-type diffusion layer forming composition to form an n-type diffusion layer on the semiconductor substrate after application of the n-type diffusion layer formation composition;
Forming an electrode on the formed n-type diffusion layer;
The manufacturing method of the solar cell element which has this.

The present invention can be applied to a solar cell element using a semiconductor substrate and can form a uniform n-type diffusion layer in a specific region without forming an n-type diffusion layer in an unnecessary region. It is possible to provide a diffusion layer forming composition, a method for producing an n-type diffusion layer using the composition, and a method for producing a solar cell element.

It is sectional drawing which shows notionally an example of the manufacturing process of a solar cell element. 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 solar cell element of FIG.

First, an embodiment of the n-type diffusion layer forming composition of the present invention will be described, and then an embodiment of an n-type diffusion layer manufacturing method and a solar cell element manufacturing method using the n-type diffusion layer forming composition will be described. .
In the present specification, the term “process” is not limited to an independent process, and even if it cannot be clearly distinguished from other processes, the term “process” is used as long as the intended purpose of the process is achieved. included. In the present specification, “˜” indicates a range including the numerical values described before and after the values as the minimum value and the maximum value, respectively. Furthermore, in this specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. means.
In this specification, the term “layer” includes a configuration formed in a part in addition to a configuration formed in the entire surface when observed as a plan view.

<N-type diffusion layer forming composition>
The n-type diffusion layer forming composition of the present embodiment contains a glass powder containing a donor element and having a particle diameter d90 of 0.1 μm to 1.5 μm, and a dispersion medium. The n-type diffusion layer forming composition of the present embodiment may further contain other additives as necessary in consideration of suitability (applicability) of the composition.
Here, the n-type diffusion layer forming composition contains at least a glass powder containing a donor element, and can be formed on the semiconductor substrate by thermally diffusing the donor element after being applied to the semiconductor substrate. Say material.

By using an n-type diffusion layer forming composition containing a donor element and containing a glass powder having a particle diameter d90 of 0.1 μm to 1.5 μm, the semiconductor in the coating region of the n-type diffusion layer forming composition during the drying process Even when the thickness of the central part in the surface direction of the substrate is reduced by the frame phenomenon, if the glass powder has a particle diameter in the above range, a high presence ratio of the glass powder can be ensured. Further, since the melting time of the glass powder can be shortened during the diffusion treatment, a glass layer having no pinhole can be formed on a micro scale. Thereby, an n-type diffusion layer having a more uniform phosphorus concentration is formed at a desired portion of the semiconductor substrate, and unnecessary n-type diffusion layers are not formed on the back surface and side surfaces of the semiconductor substrate.

Therefore, if the composition for forming an n-type diffusion layer of the present embodiment is applied, the side etching step that is essential in the gas phase reaction method widely used in the past is not necessary, 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 the choice of the manufacturing method to be applied and the material and shape of the back electrode is 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 the curvature of a semiconductor substrate is also suppressed.

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

Further, since the donor element in the glass powder is not easily volatilized even during the heat treatment (firing), the generation of the volatilizing gas suppresses the formation of n-type diffusion layers not only on the surface of the semiconductor substrate but also on the back surface and side surfaces. .
For this reason, the donor element is considered to be difficult to volatilize because it is bonded to other elements as constituent elements in the glass.

As described above, since the n-type diffusion layer forming composition of the present embodiment can form an n-type diffusion layer having a desired concentration in a desired portion of the semiconductor substrate, an n-type donor element (dopant). It is possible to form a selective region having a high concentration of. On the other hand, a selective region having a high concentration of the n-type donor element is formed by a gas phase reaction method or a method using a phosphate-containing solution or paste, which is a general method for forming an n-type diffusion layer. That is generally difficult.

The glass powder containing the donor element used in this embodiment will be described in detail.
A donor element is an element that can form an n-type diffusion layer by diffusing (doping) into a semiconductor substrate. As the donor element, a Group 15 element can be used, and examples thereof include P (phosphorus), Sb (antimony), Bi (bismuth), and As (arsenic). From the viewpoints of safety, easiness of vitrification, and the like, it is preferably at least one selected from P (phosphorus) and Sb (antimony).

As the donor element-containing substance used to introduce the donor element to the glass powder, for _example, include _{P 2 O 3, P 2 O} 5, Sb 2 O 3, Bi 2 O 3 and _{As 2 O 3, P} 2 It is preferable to use at least one selected from the group consisting of O ₃ , P ₂ O ₅ and Sb ₂ O ₃ .

Moreover, the glass powder containing a donor element can control a melting temperature, a softening temperature, a glass transition temperature, chemical durability, etc. by adjusting a component ratio as needed. It is preferable that the glass powder containing a donor element further contains a glass component substance described below.
Examples of the glass component material include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ , WO ₃ , MoO ₃ , MnO, La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , ZrO ₂ , GeO ₂ , TeO ₂ and Lu ₂ O ₃ can be mentioned, SiO ₂ , K ₂ O, Na It is preferable to use at least one selected from the group consisting of ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ , WO ₃ , MoO ₃ and MnO. _{, SiO 2, K 2 O,} Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO 2 and MoO It is more preferable to use at least one selected from the group consisting of.

Examples of the glass powder containing a donor element include a system containing both the donor element-containing substance and the glass component substance, and at least selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O _3. and one of the donor element-containing _substance, the group consisting of _{SiO 2, K 2 O, Na} 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO 2 and MoO ₃ It is preferable that the glass powder contains at least one glass component substance selected more.
Specific examples of the glass powder containing a donor element include a P ₂ O ₅ —SiO ₂ system (described in the order of a donor element-containing substance—a glass component substance, the same applies hereinafter), a P ₂ O ₅ —K ₂ O system, P ₂ O ₅ -Na _{2 O-based,} P ₂ O 5 -Li ₂ O _system, P ₂ O 5 _-BaO-based, P ₂ O 5 -SrO _based, P ₂ O 5 _-CaO-based, P ₂ O 5 -MgO-based, P ₂ O ₅ —BeO, P ₂ O ₅ —ZnO, P ₂ O ₅ —CdO, P ₂ O ₅ —PbO, P ₂ O ₅ —SnO, P ₂ O ₅ —GeO ₂ , P ₂ O ₅ -TeO ₂ system such as a donor element-containing material as a system containing _P 2 _{O 5,} and including _Sb 2 _{O 3} as a donor element-containing material instead of _P 2 _{O 5} of system containing _P 2 _{O 5} of the Glass powders such as a system are mentioned.
Note that a glass powder containing two or more kinds of donor element-containing substances, such as a P ₂ O ₅ —Sb ₂ O ₃ system and a P ₂ O ₅ —As ₂ O ₃ system, may be used.
In the above, a composite glass containing two components has been exemplified, but a glass powder containing three or more components as required may be used, such as a P ₂ O ₅ —SiO ₂ —MgO system.

The content ratio of the glass component substance in the glass powder is preferably set appropriately in consideration of the melting temperature, the softening temperature, the glass transition temperature, the chemical durability, and the like, and generally 0.1 mass% to 95 mass%. It is preferably 0.5% by mass to 90% by mass.

Specifically, the content ratio of SiO ₂ in the case of the glass powder containing SiO ₂ is preferably from 10 mass% to 90 mass%, more preferably from 10 wt% to 50 wt%, 10 More preferably, the content is from 30% by mass to 30% by mass.

The softening temperature of the glass powder is preferably 400 ° C. to 900 ° C. from the viewpoints of diffusibility during the diffusion treatment and dripping. Further, it is more preferably 600 ° C. to 800 ° C., and further preferably 700 ° C. to 800 ° C. If the softening temperature is 400 ° C. or higher, it is suppressed that the viscosity of the glass becomes too low during the diffusion treatment, and it is difficult for dripping to occur, so that the formation of the n-type diffusion layer other than the specific portion tends to be suppressed. It is in. Further, when the softening temperature is 900 ° C. or lower, it is difficult for the glass powder to be completely melted, and a uniform n-type diffusion layer tends to be formed.
If the softening temperature of the glass powder is in the range of 400 ° C. to 900 ° C., no dripping will occur, so that it is possible to form an n-type diffusion layer in a desired shape in a specific region after the diffusion treatment. Become. For example, when the n-type diffusion layer forming composition is applied in a linear pattern having a width of a μm, the linear width b after the diffusion treatment can hold a linear pattern in the range of b <1.5 a μm.

The softening temperature of the glass powder can be obtained from a differential heat (DTA) curve or the like using a DTG-60H type differential heat / thermogravimetric simultaneous measuring device manufactured by Shimadzu Corporation.

Examples of the shape of the glass powder include a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like, and a coating property (applicability to the substrate) and uniform diffusibility when an n-type diffusion layer forming composition is used. From this point, it is desirable that the shape is substantially spherical, flat or plate-like.

The particle diameter d90 of the glass powder needs to be 0.1 μm to 1.5 μm. Further, it is preferably 0.2 μm to 0.5 μm, and more preferably 0.2 μm to 0.3 μm.
By setting the particle diameter d90 of the glass powder to 1.5 μm or less, even in the area where the thickness in the coating area is thin during the drying process, the presence ratio of the glass powder is high, and the glass powder can be melted in a short time. It becomes easy to obtain a glass layer that is not present. Therefore, the semiconductor substrate can be covered more uniformly with the glass layer, and a more uniform n-type diffusion layer can be formed without unevenness in the diffused donor element concentration.
In this embodiment, the larger the glass particle diameter, the more difficult it is to melt and the non-uniform glass layer. Therefore, attention is paid to the value of the particle diameter d90 in order to finely mix the glass having a large particle diameter.

Whether a uniform n-type diffusion layer is formed can be determined by, for example, subjecting the semiconductor substrate on which the n-type diffusion layer is formed to a thermal oxidation treatment at 900 ° C. to 1000 μm or more formed on the semiconductor substrate in the n-type diffusion layer region. This can be confirmed by the variation of the oxide film of about 3000 mm. In general, the oxidation rate on the surface of a semiconductor substrate depends on the concentration of the diffused donor element. Therefore, when there is a region where the donor element is not sufficiently diffused, the variation of the oxide film thickness increases in the plane of the semiconductor substrate. In the present embodiment, the thickness of the oxide film is measured using an ellipsometer MARY-102 manufactured by Fibravo. The variation of the oxide film can be confirmed by measuring nine points in the plane and the ratio between the maximum value and the minimum value (maximum value / minimum value). For example, the variation in the oxide film thickness can be evaluated as a uniform n-type diffusion layer formed when the ratio (maximum value / minimum value) is 1.00 to 1.10. Further, the color of the oxide film is observed using an optical microscope, and it can be confirmed that the oxide film is uniformly formed from the uneven color. When no color unevenness occurs in the plane, it can be evaluated that a uniform n-type diffusion layer is formed on a microscale.
Here, the micro scale indicates a range of 1 μm to 10 μm in the surface direction or thickness direction of the semiconductor substrate.

Here, the particle diameter d90 refers to the particle diameter at which 90% of the total particle diameter is accumulated sequentially from the smallest particle diameter when a volume distribution integrated curve of particle diameter is drawn. The volume distribution integrated curve can be measured with a laser scattering diffraction particle size distribution analyzer (manufactured by Beckman Coulter, Inc.) or the like.

The average particle diameter d50 of the glass powder used in this embodiment is preferably 0.05 μm to 0.5 μm. The average particle diameter d50 is more preferably 0.05 μm to 0.3 μm, and even more preferably 0.05 μm to 0.2 μm. The average particle diameter d50 of the glass powder represents a volume average particle diameter, and can be measured by a laser scattering diffraction particle size distribution analyzer (manufactured by Beckman Coulter, Inc.).

The glass powder containing a donor element is produced by the following procedure.
First, raw materials, for example, a donor element-containing material and a glass component material are weighed and filled in a crucible. Examples of the crucible material include platinum, platinum-rhodium, 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 donor element-containing material and the glass component material are heated to a melt by a temperature corresponding to the glass composition in an electric furnace. 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 powder. A known method such as a jet mill, a bead mill, or a ball mill can be applied to the pulverization.

The content ratio of the glass powder containing the donor element in the n-type diffusion layer forming composition is determined in consideration of application suitability (applicability), diffusibility of the donor element, and the like. In general, the content ratio of the glass powder in the n-type diffusion layer forming composition is preferably 0.1% by mass to 95% by mass, more preferably 1% by mass to 90% by mass. The content is more preferably 5% by mass to 85% by mass, and particularly preferably 2% by mass to 80% by mass.
Further, the content ratio of the metal particles in the n-type diffusion layer forming composition is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less.

Next, the dispersion medium will be described.
A dispersion medium is a medium in which glass powder containing a donor element is dispersed in a composition. Specifically, at least one selected from the group consisting of a binder and a solvent is employed as the dispersion medium.

Examples of the binder include polyvinyl alcohol, polyacrylamide, polyvinyl amide, polyvinyl pyrrolidone, polyethylene oxide, polysulfonic acid, acrylamide alkyl sulfonic acid, cellulose ether, cellulose derivative, carboxymethyl cellulose, hydroxyethyl cellulose, ethyl cellulose, gelatin, starch and starch derivative, Sodium alginate and sodium alginate derivatives, xanthan and xanthan derivatives, guar gum and guar gum derivatives, scleroglucan and scleroglucan derivatives, tragacanth and tragacanth derivatives, dextrin and dextrin derivatives, poly (meth) acrylic acid, poly (meth) acrylic acid ester (For example, polyalkyl (meth) acrylate, polydimethyl Ruaminoechiru (meth) acrylate), polybutadiene, polystyrene, and copolymers thereof. In addition, polysiloxane can be appropriately selected. These are used singly or in combination of two or more.

The molecular weight of the binder (for example, the weight average molecular weight) is not particularly limited, and it is desirable to appropriately adjust in view of the desired viscosity as the composition.

Solvents include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-i-propyl ketone, methyl-n-butyl ketone, methyl-i-butyl ketone, methyl-n-pentyl ketone, methyl-n-hexyl ketone, diethyl ketone , Ketone solvents such as dipropyl ketone, di-i-butyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n- Propyl ether, di-i-propyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol Di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di- n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl-n-butyl ether, triethylene glycol di-n-butyl ether, triethylene Glycol meth -N-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl-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 methyl-n- Butyl ether, dipropylene glycol di -N-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl ethyl ether, tripropylene glycol methyl-n- Butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetrapropylene glycol methyl-n-butyl ether, tetrapropylene Glycolmethyl-n-hexyl ether, tetrapropylene Ether solvents such as glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, s-butyl acetate, n-pentyl acetate, s-acetate Pentyl, 3-methoxybutyl acetate, methyl pentyl 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, diethylene glycol methyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether acetate, glycol diacetate, methoxytriethylene glycol acetate, propion Ethyl, n-butyl propionate, i-amyl 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, diethylene glycol mono-n-butyl ether acetate, γ-butyrolactone, Ester solvents such as γ-valerolactone; acetonitrile, N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propyl Aprotic polar solvents such as loridinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide; methanol, ethanol, n-propanol, i -Propanol, n-butanol, i-butanol, s-butanol, t-butanol, n-pentanol, i-pentanol, 2-methylbutanol, sec-pentanol, t-pentanol, 3-methoxybutanol, n -Hexanol, 2-methylpentanol, s-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, s-octanol, n-nonyl alcohol, n-decanol, s-undecylal Cole, 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 Alcohol solvents such as triethylene glycol and tripropylene glycol; 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, ethoxytriglycol, te Glycol monoether solvents such as raethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether; terpinene, terpineol, myrcene, alloocimene, limonene, dipentene Terpene solvents such as pinene, carvone, ocimene, and ferrandrene; water and the like. These are used singly or in combination of two or more. In the case of an n-type diffusion layer forming composition, from the viewpoint of applicability to the substrate, at least one selected from the group consisting of terpineol, diethylene glycol mono-n-butyl ether and diethylene glycol mono-n-butyl ether acetate is preferred, and terpineol and At least one selected from diethylene glycol mono-n-butyl ether is a more preferable solvent.

The content ratio of the dispersion medium in the n-type diffusion layer forming composition is determined in consideration of applicability, donor concentration, and the like.
The viscosity of the n-type diffusion layer forming composition is preferably 10 mPa · s to 1000000 mPa · s at 25 ° C., more preferably 50 mPa · s to 200000 mPa · s at 25 ° C. in consideration of applicability. More preferably, it is s to 100,000 mPa · s.
The viscosity of the n-type diffusion layer forming composition is measured at 25 ° C. using an E-type viscometer (manufactured by Tokyo Keiki Co., Ltd.) at a rotation speed of 5 rpm (min ⁻¹ ).

Furthermore, the n-type diffusion layer forming composition may contain other additives as necessary. Other additives include organometallic compounds, silane coupling agents, organic fillers, inorganic fillers, thixotropic agents such as organic acid salts, wettability improvers, leveling agents, surfactants, plasticizers, fillers, Examples include antifoaming agents, stabilizers, antioxidants, and fragrances. Other additives can be used in an amount of about 0.01 to 20 parts by mass with respect to 100 parts by mass of the total amount of the n-type diffusion layer forming composition. Moreover, these can be used individually or in combination of 2 or more types.

<The manufacturing method of an n type diffused layer, and the manufacturing method of a solar cell element>
The method for producing an n-type diffusion layer according to this embodiment includes a step of applying the n-type diffusion layer forming composition on a semiconductor substrate and a thermal diffusion on the semiconductor substrate after the application of the n-type diffusion layer forming composition. And a step of performing a process.
Moreover, the manufacturing method of the solar cell element of this embodiment includes the step of applying the n-type diffusion layer forming composition on a semiconductor substrate, and the thermal diffusion to the semiconductor substrate after applying the n-type diffusion layer forming composition. And a step of forming an n-type diffusion layer on the semiconductor substrate after applying the n-type diffusion layer forming composition and a step of forming an electrode on the formed n-type diffusion layer. .

A method for manufacturing the n-type diffusion layer and solar cell element of the present embodiment (hereinafter, both may be collectively referred to as the manufacturing method of the present embodiment) will be described with reference to FIG. In addition, 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.
FIG. 1 is a schematic cross-sectional view conceptually showing an example of a manufacturing process of a solar cell element in the manufacturing method of the present embodiment. In FIG. 1, 10 is a p-type semiconductor substrate, 12 is an n-type diffusion layer, 14 is a p ⁺ -type diffusion layer, 16 is an antireflection film, 18 is a front electrode, and 20 is a back electrode (electrode layer). . In the subsequent drawings, common constituent elements are denoted by the same reference numerals and description thereof is omitted. Hereinafter, an example in which a silicon substrate is used as the p-type semiconductor substrate will be described, but 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 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 cell element, by forming a texture structure on the light receiving surface (surface) side, a 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. In this embodiment, there is no restriction | limiting in the application | coating method of an n type diffused layer formation composition, For example, a printing method, a spin coat method, a brush coating method, a spray method, a doctor blade method, a roll coat method, and an inkjet method are mentioned. .
The coating amount of the n-type diffusion layer forming composition is not particularly limited. For example, the glass powder amount can be 5 g / m ² to 100 g / m ^2, and it can be 10 g / m ² to 50 g / m ^2. Is preferred. In particular, the coating thickness may be thin at 5 g / m ² to 15 g / m ² , but when the particle diameter d90 of the glass powder is 0.1 μm to 1.5 μm, the glass layer does not penetrate during the diffusion treatment, A more uniform n-type diffusion layer can be formed on a scale.

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, drying is performed at a temperature of about 80 ° C. to 300 ° C. for about 1 to 10 minutes when using a hot plate, and about 10 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 in the present embodiment.

When the manufacturing method of the present embodiment is used, the manufacturing method of the p ⁺ -type diffusion layer (high concentration electric field layer) 14 on the back surface is a method based on conversion from an n-type diffusion layer to a p + -type diffusion layer by aluminum. Without limitation, any conventionally known method can be adopted, and the options of the manufacturing method are expanded. Therefore, for example, the composition 13 containing a Group 13 element such as B (boron) is applied to the back surface of the p-type semiconductor substrate 10 (the surface opposite to the surface to which the n-type diffusion layer forming composition is applied). , P ⁺ -type diffusion layer 14 can be formed.
As the composition 13 containing a Group 13 element such as B (boron), for example, a glass powder containing an acceptor element is used instead of a glass powder containing a donor element, and the composition 13 is made in the same manner as the n-type diffusion layer forming composition. A p-type diffusion layer forming composition may be mentioned. The acceptor element may be a Group 13 element, and examples thereof include B (boron), Al (aluminum), and Ga (gallium). Further, it is preferable that the glass powder containing acceptor element comprising at least one member selected from the group consisting of _{B 2 O 3, Al 2 O} 3 and _Ga 2 _{O 3.}
Furthermore, the method for applying the p-type diffusion layer forming composition to the back surface of the silicon substrate is the same as the method for applying the n-type diffusion layer forming composition described above to the silicon substrate.

The semiconductor substrate granted the p-type diffusion layer forming composition on the back side, similarly to the thermal diffusion treatment of the applied semiconductor substrate of n-type diffusion layer forming composition described below by a thermal diffusion process, p on the back ⁺ The mold diffusion layer 14 can be formed. The thermal diffusion treatment of the p-type diffusion layer forming composition is preferably performed simultaneously with the thermal diffusion treatment of the n-type diffusion layer forming composition.

Next, the p-type semiconductor substrate 10 on which the n-type diffusion layer forming composition layer 11 is formed is subjected to a thermal diffusion treatment at a temperature not lower than the melting point of the glass powder in the n-type diffusion layer forming composition, for example, 600 ° C. to 1200 ° C. By this thermal diffusion treatment, as shown in FIG. 1C, the donor element diffuses into the semiconductor substrate, 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. Further, the furnace atmosphere during the thermal diffusion treatment can be appropriately adjusted to air, oxygen, nitrogen or the like.
The thermal diffusion treatment time can be appropriately selected according to the content ratio of the glass powder containing the donor element contained in the n-type diffusion layer forming composition. For example, it can be 1 minute to 60 minutes, and preferably 2 minutes to 30 minutes.

A glass layer (not shown) such as phosphate glass is formed on the surface of the formed n-type diffusion layer 12. For this reason, this phosphate glass is removed by etching. As the etching, any of known methods such as a method of immersing the p-type semiconductor substrate 10 in an acid such as hydrofluoric acid and a method of immersing the p-type semiconductor substrate 10 in an alkali such as caustic soda can be applied. When using an etching method in which the p-type semiconductor substrate 10 is immersed in an acid such as hydrofluoric acid, the immersion time is not particularly limited and is generally 0.5 minutes to 30 minutes, preferably 1 minute to 10 minutes. Can do.

In the manufacturing method of the present embodiment shown in FIGS. 1 (2) and (3), the n-type diffusion layer 12 is formed at a desired site, and unnecessary n-type diffusion layers are not formed on the back surface and side surfaces.
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 embodiment, the side etching process becomes unnecessary, and the process is simplified. As described above, by the manufacturing method of the present embodiment, a more uniform n-type diffusion layer having a desired shape is formed in a desired portion in a short time.

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, there is a method in which an n-type diffusion layer on the back surface is coated with a paste of aluminum which is a Group 13 element, baked, and aluminum is diffused into the n-type diffusion layer to convert it into a p + -type diffusion layer. It has been adopted. In this method, in order to make sufficient conversion to the p ⁺ type diffusion layer and to form a high concentration electric field layer of the p ⁺ type diffusion layer, an aluminum amount of a certain amount or more is required. It was necessary to form it thickly. 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. In addition, the warpage easily damages the solar cell element when the solar cell element is transported in the module process and when the solar cell element is connected to a copper wire called a tab wire. 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 manufacturing method of the present embodiment, since an unnecessary n-type diffusion layer is not formed on the back surface, it is not necessary to convert the n-type diffusion layer to the p + -type diffusion layer, and it is necessary to increase the thickness of the aluminum layer. Disappears. 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.

When the manufacturing method of the present embodiment is used, the manufacturing method of the p ⁺ -type diffusion layer (high concentration electric field layer) 14 on the back surface is a method based on conversion from an n-type diffusion layer to a p + -type diffusion layer by aluminum. Without limitation, any conventionally known method can be adopted, and the options of the manufacturing method are expanded.
For example, using a glass powder containing an acceptor element instead of a glass powder containing a donor element, a p-type diffusion layer forming composition configured in the same manner as the n-type diffusion layer forming composition is applied to the back surface of the silicon substrate. Then, it is preferable to form a p ⁺ -type diffusion layer (high-concentration electric field layer) 14 on the back surface by firing treatment.
As will be described later, the material used for the back electrode 20 is not limited to Group 13 aluminum, and Ag (silver), Cu (copper), or the like can be applied. Can also be formed thin.

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 mixed gas flow ratio NH ₃ / SiH ₄ is 0.05 to 1.0, the reaction chamber pressure is 13.3 Pa (0.1 Torr) to 266.6 Pa (2 Torr), and the temperature during film formation The silicon nitride film is formed under the conditions of 300 ° C. to 550 ° C. and a frequency for plasma discharge 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. The metal paste for a surface electrode contains (1) metal particles and (2) glass particles as essential components, and includes (3) a resin binder and (4) other additives as necessary.

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 this embodiment, 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, you may provide the silver paste layer for silver electrode formation in a part of back surface for the connection between the solar cell elements in a module process.

1 (6), the electrode metal paste layer 17 is fired to complete the solar cell element. When baked 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 a part of the surface of the p-type semiconductor substrate 10 is also partially formed. When melted, the metal particles (for example, silver particles) in the paste form a contact portion with the p-type semiconductor substrate 10 and solidify. 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.

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. 2 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. It is a perspective view which expands and shows a part of solar cell element.

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, vapor deposition of an electrode material by electron beam heating in a high vacuum, and the like. 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 the diffusion layer forming composition is used, a back contact type solar cell element can be produced.
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 embodiment can form an n-type diffusion site at a specific site. Therefore, the n-type diffusion layer forming composition of the present embodiment can be suitably applied to the production of the back contact type solar cell element.

In the present embodiment, the use of the n-type diffusion layer forming composition in the manufacture of an n-type diffusion layer, and the n-type diffusion layer in the manufacture of a solar cell element including the semiconductor substrate, the n-type diffusion layer, and an electrode The use of forming compositions is also encompassed. As described above, by using the n-type diffusion layer forming composition of the present embodiment, a desired shape can be obtained in a specific region in a short time without forming an unnecessary n-type diffusion layer, and on a microscale. A uniform n-type diffusion layer can be obtained. Moreover, a solar cell element having such an n-type diffusion layer can be obtained without forming an unnecessary n-type diffusion layer.

Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. Unless otherwise stated, all chemicals used reagents. “%” Means “% by mass” unless otherwise specified. Further, “cm / s” means “linear velocity” obtained by dividing the flow rate of the gas flowing into the furnace by the cross-sectional area of the electric furnace unless otherwise specified.

[Example 1]
P ₂ O ₅ —SiO ₂ —MgO-based glass (softening temperature 700 ° C., P ₂ O ₅ : 58.58) having a substantially spherical particle shape, an average particle diameter d50 of 0.15 μm, and a particle diameter d90 of 0.25 μm. 2%, SiO ₂ : 29.7%, MgO: 12.1%) 7.5 g of powder, 2.5 g of ethyl cellulose, and 40.0 g of terpineol were mixed using an automatic mortar kneader to make a paste, An n-type diffusion layer forming composition was prepared.

The shape of the glass powder was determined by observing with a TM-1000 scanning electron microscope manufactured by Hitachi High-Technologies Corporation. The average particle diameter d50 and particle diameter d90 of the glass powder were calculated using an LS 13 320 type laser scattering diffraction particle size distribution analyzer (measurement wavelength: 632 nm) manufactured by Beckman Coulter, Inc.

Next, the prepared paste was applied to the surface of the p-type silicon substrate by screen printing so as to have a range of 45 mm × 45 mm, and dried on a hot plate at 150 ° C. for 5 minutes. Subsequently, a thermal diffusion treatment is performed by holding in an electric furnace set at 950 ° C. for 20 minutes in an air flow (0.9 cm / s) atmosphere, and then the substrate is immersed in hydrofluoric acid for 5 minutes to remove the glass layer. And washed with running water. Thereafter, drying was performed.

The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 12Ω / □, P (phosphorus) was diffused, and an n-type diffusion layer was formed. On the other hand, the sheet resistance on the back surface was 1000000 Ω / □ or more, which was not measurable, and the n-type diffusion layer was not 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.

The silicon substrate on which the n-type diffusion layer was formed was thermally oxidized by holding it in an electric furnace set at 900 ° C. in an oxygen flow (0.9 cm / s) atmosphere for 180 minutes to form an oxide film. . In the region where the n-type diffusion layer was formed, the in-plane oxide film thickness variation σ was 1.03, and a uniform n-type diffusion layer was formed.
σ represents a ratio of maximum film thickness / minimum film thickness, and was calculated from nine oxide film thicknesses in the coated surface. The thickness of the oxide film was measured using an ellipsometer MARY-102 manufactured by Fibravo.

[Example 2]
An n-type diffusion layer was formed in the same manner as in Example 1 except that the average particle diameter d50 of the glass powder was 0.22 μm and the particle diameter d90 was 0.40 μm.
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 13Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. On the other hand, the sheet resistance on the back surface was 1000000 Ω / □ or more, which was not measurable, and the n-type diffusion layer was not formed. Further, the variation σ of the oxide film thickness formed on the n-type diffusion layer was 1.04, and a uniform n-type diffusion layer was formed.

[Example 3]
An n-type diffusion layer was formed in the same manner as in Example 1 except that the average particle diameter d50 of the glass powder was 0.35 μm and the particle diameter d90 was 0.80 μm.
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 13Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. On the other hand, the sheet resistance on the back surface was 1000000 Ω / □ or more, which was not measurable, and the n-type diffusion layer was not formed. The variation σ of the oxide film thickness formed on the n-type diffusion layer was 1.05, and a uniform n-type diffusion layer was formed.

[Example 4]
P ₂ O ₅ —SiO ₂ —MgO-based glass having an average particle diameter d50 of 0.15 μm and a particle diameter d90 of 0.25 μm (softening temperature 700 ° C., P ₂ O ₅ : 58.2%, SiO ₂ : 29 .7%, MgO: 12.1%) n-type diffusion layer using 15 g of powder, 2.5 g of ethylcellulose, 31 g of terpineol, and 1.5 g of silane coupling agent KBM602 (manufactured by Shin-Etsu Chemical Co., Ltd.) An n-type diffusion layer was formed in the same manner as in Example 1 except that the forming composition was prepared.
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 10Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. On the other hand, the sheet resistance on the back surface was 1000000 Ω / □ or more, which was not measurable, and the n-type diffusion layer was not formed. Further, the variation σ of the oxide film thickness formed on the n-type diffusion layer was 1.04, and a uniform n-type diffusion layer was formed.

[Example 5]
P ₂ O ₅ —SiO ₂ —MgO glass having an average particle diameter d50 of 0.15 μm and a particle diameter d90 of 0.25 μm (softening temperature 650 ° C., P ₂ O ₅ : 61.0%, SiO ₂ : 25 0.1% MgO: 13.9%) n-type diffusion layer using 15 g of powder, 2.5 g of ethylcellulose, 31 g of terpineol, and 1.5 g of silane coupling agent KBM602 (manufactured by Shin-Etsu Chemical Co., Ltd.) An n-type diffusion layer was formed in the same manner as in Example 1 except that the forming composition was prepared.
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 10Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. On the other hand, the sheet resistance on the back surface was 1000000 Ω / □ or more, which was not measurable, and the n-type diffusion layer was not formed. The variation σ of the oxide film thickness formed on the n-type diffusion layer was 1.03, and a uniform n-type diffusion layer was formed.

[Comparative Example 1]
An n-type diffusion layer was formed in the same manner as in Example 1 except that the average particle diameter d50 of the glass powder was 0.57 μm and the particle diameter d90 was 2.55 μm.
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 15Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. On the other hand, the sheet resistance on the back surface was 1000000 Ω / □ or more, which was not measurable, and the n-type diffusion layer was not formed. However, the variation σ of the oxide film thickness formed on the n-type diffusion layer was 1.55, and the n-type diffusion layer was not uniform. When the color of the oxide film thickness was observed using an optical microscope, there was a region having a 3 μm square and a different color of the oxide film, and the variation of the oxide film thickness was confirmed.

[Comparative Example 2]
An n-type diffusion layer was formed in the same manner as in Example 1 except that the average particle diameter d50 of the glass powder was 0.30 μm and the particle diameter d90 was 1.60 μm.
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 13Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. On the other hand, the sheet resistance on the back surface was 1000000 Ω / □ or more, which was not measurable, and the n-type diffusion layer was not formed. However, the variation σ of the oxide film thickness formed on the n-type diffusion layer was 1.35, and the n-type diffusion layer was non-uniform. When the color of the oxide film thickness was observed using an optical microscope, the color of the oxide film was slightly different at 2 μm square, and the variation of the oxide film thickness was confirmed.

[Comparative Example 3]
An n-type diffusion layer was formed in the same manner as in Example 1 except that ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) powder was used instead of P ₂ O ₅ —SiO ₂ —MgO glass powder. .
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 20Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. However, the sheet resistance on the back surface was 20Ω / □, and an n-type diffusion layer was also formed on the back surface.

It should be noted that the entire disclosure of the Japanese application 2014-2222012 is incorporated herein by reference. In addition, all the documents, patent applications, and technical standards described in this specification are the same as when individual documents, patent applications, and technical standards are specifically and individually described to be incorporated by reference. Which is incorporated herein by reference.

Claims (6)

1. An n-type diffusion layer forming composition comprising a glass powder containing a donor element and having a particle diameter d90 of 0.1 μm to 1.5 μm and a dispersion medium.
2. 2. The n-type diffusion layer forming composition according to claim 1, wherein the glass powder has an average particle diameter d50 of 0.05 μm to 0.5 μm.
3. The n-type diffusion layer forming composition according to claim 1 or 2, wherein the donor element is at least one selected from P (phosphorus) and Sb (antimony).
4. The glass powder includes at least one donor element-containing material selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ , SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O. , BaO, SrO, CaO, MgO , BeO, ZnO, PbO, CdO, SnO, claim comprising at least one glass component material selected from the group consisting of ZrO ₂ and MoO _3, from 1 to claim 3 The n type diffused layer formation composition of any one of these.
5. Applying the n-type diffusion layer forming composition according to any one of claims 1 to 4 on a semiconductor substrate;
   Applying a thermal diffusion treatment to the semiconductor substrate after the application of the n-type diffusion layer forming composition;
   The manufacturing method of the n type diffused layer which has this.
6. Applying the n-type diffusion layer forming composition according to any one of claims 1 to 4 on a semiconductor substrate;
   Applying a thermal diffusion treatment to the semiconductor substrate after application of the n-type diffusion layer forming composition to form an n-type diffusion layer on the semiconductor substrate after application of the n-type diffusion layer formation composition;
   Forming an electrode on the formed n-type diffusion layer;
   The manufacturing method of the solar cell element which has this.

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