TW201419384A - Composition for forming n-type diffusion layer, method for forming n-type diffusion layer, and method for producing photovoltaic cell - Google Patents

Abstract

The present invention provides a composition for forming an n-type diffusion layer, the composition including a glass powder containing a donor element and having an average particle diameter of 5 μ m or less and a softening temperature of from 500 DEG C to 900 DEG C, and the composition also including a dispersion medium.

Description

N-type diffusion layer forming composition, manufacturing method of n-type diffusion layer, and solar power Cell component manufacturing method

The present invention relates to an n-type diffusion layer forming composition of a solar cell element, a method of manufacturing an n-type diffusion layer, and a method of manufacturing a solar cell element. More specifically, the present invention relates to a semiconductor substrate. A technique in which a specific region of germanium forms an n-type diffusion layer.

The manufacturing steps of the prior 矽 solar cell element will be described.

First, in order to promote the light confinement effect and to increase the efficiency, a p-type ruthenium substrate having a texture structure formed on the light-receiving surface is prepared, and then phosphorus oxychloride (POCl ₃ ) as a compound containing a donor element is prepared. The n-type diffusion layer was formed in the same manner in a mixed gas atmosphere of nitrogen and oxygen at a temperature of 800 ° C to 900 ° C for several tens of minutes. In this prior method, since phosphorus is diffused by using a mixed gas, an n-type diffusion layer is formed not only on the surface but also on the side surface and the back surface. Therefore, a side etching step for removing the side n-type diffusion layer is required. Further, the n-type diffusion layer on the back surface must be converted into a p ⁺ -type diffusion layer, and an aluminum paste is applied to the n-type diffusion layer on the back surface, and is converted from the n-type diffusion layer into a p ⁺ -type diffusion layer by diffusion of aluminum.

On the other hand, in the field of semiconductor manufacturing, there has been proposed a method of coating a phosphate containing phosphorus pentoxide (P ₂ O ₅ ) or ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) as a solution. A solution of a compound of a donor element is formed to form an n-type diffusion layer (for example, refer to JP-A-2002-75894). Further, in order to form a diffusion layer, a technique in which a paste containing phosphorus as a donor element is applied as a diffusion source on the surface of a ruthenium substrate and thermally diffused to form a diffusion layer is also known (for example, refer to Japanese Patent No. 4,037,968). Bulletin).

However, in these methods, the donor element or the compound containing the same is self-expanding The scattered solution or the paste scatters. Therefore, similar to the gas phase reaction method using the above mixed gas, phosphorus diffuses to the side surface and the back surface when the diffusion layer is formed, and an n-type diffusion layer is formed in addition to the applied portion. . Moreover, generally, the upper surface of a semiconductor substrate, such as a tantalum board used for a solar cell, has a texture structure in which the height difference of a convex part and a recessed part is about 5 micrometer. Since it is applied to the surface of such a texture structure, the n-type diffusion layer may be formed unevenly.

Thus, when the n-type diffusion layer is formed, in the gas phase reaction using phosphorus oxychloride, an n-type diffusion layer is formed not only on the side (usually the light-receiving surface or surface) where the n-type diffusion layer is originally required, but also on the other side. An n-type diffusion layer is also formed on the non-light-receiving surface or the back surface or on the side surface. Further, in the method of applying a solution containing a phosphorus-containing compound or a paste and thermally diffusing, an n-type diffusion layer is formed in addition to the surface, similarly to the gas phase reaction method. Therefore, in order to have a pn junction structure, it is necessary to perform etching on the side surface and convert the n-type diffusion layer into a p-type diffusion layer on the back surface. Usually, a paste of aluminum as a Group 13 element is coated on the back surface and calcined to convert the n-type diffusion layer into a p-type diffusion layer. Further, phosphorus is unevenly diffused when the solution is applied, and a non-uniform n-type diffusion layer is formed, resulting in a decrease in conversion efficiency of the entire solar cell. Further, in a method known as a method of applying a paste containing a donor element such as phosphorus as a diffusion source, a compound containing a donor element is sublimated and vaporized, and is diffused outside a region where diffusion is required, so that it is difficult to select The diffusion layer is formed sexually in a specific area.

The present invention has been made in view of the above problems, and an object of the invention is to provide 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, wherein the n-type diffusion layer is formed. The object can be applied to a solar cell element using a semiconductor substrate, an n-type diffusion layer is formed not in an unnecessary region, and a uniform n-type diffusion layer can be formed in a specific region in a short time.

The means to solve the above problems are as follows.

<1> An n-type diffusion layer forming composition comprising: a glass powder containing a donor element and having a softening temperature of 500 ° C or more and 900 ° C or less and an average particle diameter of 5 μm or less; and a dispersing medium.

<2> The n-type diffusion layer forming composition according to the invention, wherein the glass powder has a d90 of 20 μm or less.

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

The n-type diffusion layer forming composition according to any one of <1> to <3> wherein the glass powder containing the above-mentioned donor element comprises: selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb At least one substance containing a donor element in the group consisting of ₂ O _{3 and} selected from the group consisting of SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, At least one glass component substance in a group consisting of PbO, CdO, SnO, ZrO ₂ and MoO ₃ .

<5> A method for producing an n-type diffusion layer, comprising: a step of forming an n-type diffusion layer forming composition according to any one of <1> to <4> on a semiconductor substrate; The semiconductor substrate is subjected to a step of thermal diffusion treatment.

<6> A method for producing a solar cell element, comprising: a step of forming an n-type diffusion layer forming composition according to any one of <1> to <4> on a semiconductor substrate; and applying the semiconductor after the imparting a step of forming a n-type diffusion layer by performing thermal diffusion treatment on the substrate; and forming an electrode on the n-type diffusion layer formed.

The use of the n-type diffusion layer forming composition according to any one of <1> to <4>, which produces an n-type diffusion layer.

The use of the n-type diffusion layer forming composition according to any one of <1> to <4>, which manufactures a solar cell element including a semiconductor substrate, an n-type diffusion layer, and an electrode.

According to the present invention, it is possible to provide an n-type diffusion layer forming composition, a method of manufacturing an n-type diffusion layer, and a method of manufacturing a solar cell element, wherein the n-type diffusion layer forming composition can be applied to a solar cell element using a semiconductor substrate, An n-type diffusion layer is formed in an unnecessary region, and a uniform n-type diffusion layer can be formed in a specific region in a short time.

1‧‧‧Interlayer insulating film

2‧‧‧Barrier layer

3‧‧‧ wiring metal layer

4‧‧‧Erosion

5‧‧‧ State before grinding

6‧‧‧near the wiring metal part of the interlayer insulating film

7‧‧‧ crack

A‧‧‧Abrasion

B‧‧‧Maximum amount of grinding

C‧‧‧ distance

(1) to (6) of Fig. 1 are cross-sectional views conceptually showing an example of a manufacturing procedure of a solar cell element of the present invention.

Figure 2A is a plan view of a solar cell component as viewed from the surface.

Fig. 2B is a perspective view showing a part of Fig. 2A in an enlarged manner.

First, the n-type diffusion layer forming composition of the present invention will be described, and next, an n-type diffusion layer using a n-type diffusion layer forming composition and a method for manufacturing a solar cell element will be described. Description.

Furthermore, in the present specification, the term "step" means not only an independent step, but also cannot be clearly distinguished from other steps, and is included in the term as long as the intended effect of the step is achieved. In the present specification, "~" means a range including the numerical values described before and after the minimum value and the maximum value. Further, in the present specification, when the amount of each component in the composition is such that a plurality of substances corresponding to the respective components are present in the composition, the plurality of components present in the composition are not included unless otherwise specified. The total amount of matter.

The n-type diffusion layer forming composition of the present invention includes a glass powder having at least a donor element and having a softening temperature of 500 ° C or more and 900 ° C or less and an average particle diameter of 5 μm or less (hereinafter, simply referred to as "glass powder"). In addition, as for the dispersing medium, the suitability (coating property) of the composition, and the like may be considered, and other additives may be contained as needed.

Here, the n-type diffusion layer forming composition is a material including a glass powder containing a donor element and having a softening temperature of 500 ° C or more and 900 ° C or less and an average particle diameter of 5 μm or less, which is imparted to the semiconductor. The donor element is thermally diffused on the substrate, whereby an n-type diffusion layer can be formed.

By using an n-type diffusion layer including a glass powder having a donor element and having a softening temperature of 500 ° C or more and 900 ° C or less and an average particle diameter of 5 μm or less, the viscosity of the glass during thermal diffusion treatment does not become Too low, in addition, the glass powder melts in a short time. Thereby, an n-type diffusion layer is formed at a desired portion, and an unnecessary n-type diffusion layer is not formed on the back surface or the side surface.

Therefore, if the n-type diffusion layer of the present invention is used to form a composition, the side etching step necessary in the gas phase reaction method which has been widely used previously is not required, so that the steps are simplified. Further, there is no need to convert the n-type diffusion layer formed on the back surface into a p ⁺ -type diffusion layer. Therefore, the method of forming the p ⁺ -type diffusion layer on the back surface or the material, shape, and thickness of the back surface electrode is not limited, and the selection method of the applied manufacturing method, material, and shape is expanded. In addition, generation of internal stress in the semiconductor substrate due to the thickness of the back surface electrode is suppressed, and warpage of the semiconductor substrate is also suppressed, and details will be described later.

Further, the glass powder contained in the n-type diffusion layer forming composition of the present invention is melted by calcination to form a glass layer on the n-type diffusion layer. However, in the conventional gas phase reaction method or the method of imparting a solution or paste containing a phosphate, a glass layer is also formed on the n-type diffusion layer, and therefore, the glass layer produced in the present invention can be formed in the same manner as the prior method. By etching Engraved to remove. Therefore, even if the n-type diffusion layer forming composition of the present invention does not produce an undesired product, the step is not increased as compared with the prior method.

Further, since the donor component in the glass powder is not easily sublimated during firing, it is suppressed that the n-type diffusion layer is formed not only on the surface but also on the back surface or the side surface due to the generation of the sublimation gas.

For this reason, it is considered that the donor component is strongly bonded to other elements as constituent elements in the glass, and therefore it is less volatile.

As described above, the n-type diffusion layer forming composition of the present invention can form an n-type diffusion layer having a desired concentration at a desired portion, and thus can form a selective region having a high concentration of an n-type donor element (dopant). . On the other hand, it is generally difficult to form a selective region having a high concentration of an n-type donor element by a gas phase reaction method which is a general method of an n-type diffusion layer or a method of using a solution containing a phosphate alone.

The glass powder containing the donor element of the present invention will be described in detail.

The donor element refers to an element which can form an n-type diffusion layer by being diffused (doped) in a semiconductor substrate. As the donor element, a group 15 element can be used, and examples thereof include P (phosphorus), Sb (antimony), Bi (antimony), and As (arsenic). From the viewpoints of safety, easiness of vitrification, and the like, P or Sb is suitable.

Examples of the donor element-containing substance for introducing the donor element into the glass powder include P ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ , Bi ₂ O ₃ and As ₂ O ₃ , preferably At least one selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ is used.

Further, the glass powder containing the donor element may adjust the component ratio as needed, thereby controlling the melting temperature, the softening temperature, the glass transition temperature, the chemical durability, and the like. It is preferable to further contain the glass component substance described below.

Examples of the glass component 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 , and 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 ,} etc., preferably selected from the group consisting of SiO ₂ and K ₂ At least one of a group consisting of O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ , WO ₃ , MoO ₃ and MnO, Preferably, it is selected from 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 . At least one.

Specific examples of the glass powder containing the donor element include a system containing both the donor element-containing substance and the glass component substance, and examples thereof include a P ₂ O ₅ —SiO ₂ system (including a donor element). The order of the substance-glass component is described below, P ₂ O ₅ -K ₂ O, P ₂ O ₅ -Na ₂ O, P ₂ O ₅ -Li ₂ O, P ₂ O ₅ -BaO , P ₂ O ₅ -SrO-based, P ₂ O ₅ -CaO-based, P ₂ O ₅ -MgO-based, P ₂ O ₅ -BeO-based, P ₂ O ₅ -ZnO-based, P ₂ O ₅ -CdO based, P ₂ O ₅ -PbO system, P ₂ O ₅ -SnO system, P ₂ O ₅ -GeO ₂ system, P ₂ O ₅ -TeO ₂ system, etc., including P ₂ O ₅ as a system containing a donor element, including Sb ₂ O _{3 is} used instead of the above-mentioned P ₂ O ₅ containing P ₂ O ₅ as a glass powder of a system containing a donor element.

Further, it may be a glass powder containing two or more kinds of substances containing a donor element, such as a P ₂ O ₅ —Sb ₂ O ₃ system or a P ₂ O ₅ —As ₂ O ₃ system.

In the above, a composite glass containing two components is exemplified, but a glass powder containing three or more components such as P ₂ O ₅ —SiO ₂ —CaO may be used as needed.

The content ratio of the glass component in the glass powder is preferably set in consideration of the melting temperature, the softening temperature, the glass transition temperature, and the chemical durability. In general, it is preferably 0.1% by mass or more and 95% by mass or less. It is 0.5% by mass or more and 90% by mass or less.

Specifically, the content ratio of SiO ₂ when SiO ₂ is contained in the glass powder is preferably in the range of 10% by mass or more and 90% by mass or less.

The softening temperature of the glass powder needs to be 500 ° C or more and 900 ° C or less from the viewpoint of the diffusibility at the time of the diffusion treatment and the dropping liquid. Further, it is preferably 600 ° C or more and 800 ° C or less, more preferably 700 ° C or more and 800 ° C or less. When the softening temperature is less than 500 ° C, the viscosity of the glass during the diffusion treatment is too low, and dripping occurs. Therefore, an n-type diffusion layer may be formed in addition to a specific portion. Further, in the case where the softening temperature is higher than 900 ° C, the glass powder may not be completely melted, and a uniform n-type diffusion layer may not be formed.

When the softening temperature of the glass powder is in the range of 500 ° C or more and 900 ° C or less, the dropping liquid does not occur as described above, so that the n-type diffusion layer can be formed into a desired region after the diffusion treatment. shape. For example, when the n-type diffusion layer forming composition is applied in a linear pattern having a width of a μm, a line pattern in which the line width b after the diffusion treatment is in the range of b < 1.5 a μm can be maintained.

The softening temperature of the glass powder can be determined by DTG-60H type differential heat manufactured by Shimadzu Corporation. Thermogravimetric simultaneous measurement device with differential thermal analysis (Differential Thermal Analysis, DTA)) is obtained by a curve or the like.

The shape of the glass powder is a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, or the like, and the coating property (adaptability) or uniformity to the substrate when the composition is formed into an n-type diffusion layer is used. From the viewpoint of diffusibility, it is desirable to have a substantially spherical shape, a flat shape, or a plate shape.

The average particle diameter of the glass powder needs to be 5 μm or less. Further, it is preferably 0.1 μm to 5 μm, more preferably 0.5 μm to 4 μm.

When the average particle diameter of the glass powder is 5 μm or less, even when the glass powder having a softening temperature within the above range is used, it is melted in a short time, and a smooth glass layer can be easily obtained. Therefore, by setting the average particle diameter of the glass powder to 5 μm or less, a uniform n-type diffusion layer can be formed.

The fact that the n-type diffusion layer is uniform can be confirmed, for example, by the deviation (standard deviation: σ) of the sheet resistance in the n-type diffusion layer obtained by coating on the semiconductor substrate. When the deviation (σ) of the sheet resistance value is, for example, 10 or less, preferably 5 or less, more preferably 2 or less, it can be evaluated that a uniform n-type diffusion layer is formed.

In the present invention, the sheet resistance was measured by a four-probe method at 25 ° C using a Loresta-EP MCP-T360 type low resistivity meter manufactured by Mitsubishi Chemical Corporation.

Further, σ is a standard deviation obtained by calculation of the square root of the value obtained by dividing the sum of the squares of the deviations of the sheet resistance values at 25 points obtained by the above-described measurement method in the applied plane. The value obtained from the number of data.

Further, generally, the upper surface of the semiconductor substrate used in the solar cell has a texture structure in which the height difference between the convex portion and the concave portion is about 5 μm. Therefore, by setting the average particle diameter of the glass powder to 5 μm or less, the followability to the surface of the concave portion is improved, so that uneven diffusion can be reduced.

Here, in the present specification, the average particle diameter of the glass means a volume average particle diameter unless otherwise specified, and a laser scattering diffraction particle size distribution measuring apparatus (Beckman Coulter) can be used. Manufacturing), etc. to determine.

The glass powder used in the present invention preferably has a d90 of 20 μm or less. Further, d90 is more preferably 15 μm or less, and still more preferably 10 μm or less. Here, d90 is a particle diameter when the volume distribution curve of the particle diameter is plotted, and the particles having the smallest particle diameter are sequentially accumulated to reach 90% of the whole. The volume distribution cumulative curve can be measured in the same manner as the above average particle diameter The measurement can be carried out by a laser scattering diffraction particle size distribution measuring apparatus (manufactured by Beckman Coulter Co., Ltd.) or the like.

When the d90 of the glass powder is 20 μm or less, the n-type diffusion layer forming composition is applied to the upper surface of the semiconductor substrate, and generation of large pores due to coarse particles is suppressed. The distribution of donor elements is more uniform.

The glass powder in the present invention requires the glass powder to have a softening temperature of 500 ° C to 900 ° C and an average particle diameter of 5 μm or less. Further, the glass powder preferably has a softening temperature of 600 ° C to 800 ° C, an average particle diameter of 0.1 μm to 5 μm, more preferably a softening temperature of the glass powder of 700 ° C to 800 ° C, and an average particle diameter of 0.5 μm to 4 μm.

Further, the glass powder preferably has a softening temperature of the glass powder of 500 ° C to 900 ° C, an average particle diameter of 5 μm or less, a d90 of 20 μm or less, more preferably a softening temperature of the glass powder of 600 ° C to 800 ° C, and an average particle diameter. It is 0.1 μm to 5 μm, d90 is 15 μm or less, and more preferably, the glass powder has a softening temperature of 700 ° C to 800 ° C, an average particle diameter of 0.5 μm to 4 μm, and d90 of 10 μm or less.

Further, the glass powder is more preferably a softening temperature of the glass powder of 600 ° C to 800 ° C, an average particle diameter of 0.1 μm to 5 μm, a d90 of 15 μm or less, and the glass powder containing the above-mentioned donor element includes a material selected from P ₂ O _{3 .} At least one substance containing a donor element in a group consisting of P ₂ O ₅ and Sb ₂ O ₃ , and selected from the group consisting of SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO At least one glass component in the group consisting of MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ and MoO ₃ , and more preferably the glass powder has a softening temperature of 700 ° C to 800 ° C, and an average particle size The glass powder having a diameter of 0.5 μm to 4 μm and a d90 of 10 μm or less and containing the above-mentioned donor element includes at least one selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ . a substance of a bulk element, and a group selected from 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 At least one glass component substance in the group.

The glass powder containing the donor element was produced by the following procedure.

First, the raw material is weighed, for example, the above-mentioned substance containing the donor element and the glass component substance are weighed, and then filled into the crucible. Examples of the material of the crucible include platinum, platinum-rhodium, ruthenium, aluminum oxide, quartz, and carbon. The material of the crucible is suitably selected in consideration of the melting temperature, the environment, and the reactivity with the molten material.

Next, the above-mentioned donor element-containing substance and glass component substance are heated by an electric furnace at a temperature corresponding to the glass composition to prepare a molten metal. At this time, it is desirable to perform stirring so that the melt becomes uniform.

Then, the obtained melt flows out onto a zirconia substrate, a carbon substrate or the like to vitrify the melt.

Finally, the glass is pulverized to form a 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 impartability (coatability), 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 or more and 95% by mass or less, more preferably 1% by mass or more, 90% by mass or less, and still more preferably 1.5% by mass. % or more and 85% by mass or less, particularly preferably 2% by mass or more and 80% by mass or less.

Next, the dispersing medium will be described.

The dispersion medium refers to a medium in which the glass powder is dispersed in the composition. Specifically, at least one selected from the group consisting of a binder and a solvent is used as a dispersion medium.

Examples of the binder include polyvinyl alcohol, polypropylene decylamine resin, polyvinyl guanamine resin, polyvinylpyrrolidone, polyethylene oxide resin, polysulfonic acid, acrylamide sulfonic acid, and fiber. Ether resin, cellulose derivative, carboxymethyl cellulose, hydroxyethyl cellulose, ethyl cellulose, gelatin, starch and starch derivatives, sodium alginate and sodium alginate derivatives, Sanxian gum and Sanxian Gum derivatives, guar gum and guar derivatives, scleroglucans and scleroglucan derivatives, tragacanth and xanthan gum derivatives, dextrin and dextrin derivatives, (meth)acrylic resins (meth) acrylate resin (for example, alkyl (meth) acrylate resin, dimethylaminoethyl (meth) acrylate resin, etc.), butadiene resin, styrene resin, and copolymers thereof . Further, in addition, a decane resin can be suitably selected. These binders may be used alone or in combination of two or more.

The molecular weight of the binder is not particularly limited, and is preferably adjusted in view of the desired viscosity as a composition.

Examples of the solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-isopropyl ketone, methyl-n-butyl ketone, methyl-isobutyl ketone, and methyl group. N-pentyl ketone, methyl-n-hexyl ketone, diethyl ketone, dipropyl ketone, di-isobutyl ketone, trimethyl fluorenone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2 a ketone solvent such as 4-pentanedione or acetonylacetone; diethyl ether, methyl ethyl Ether, methyl-n-propyl ether, di-isopropyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyl dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol - 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, two 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 Alcohol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl-n-butyl ether, triethylene glycol di-n-butyl ether, triethylene glycol methyl-n-hexyl ether, tetraethylene glycol Methyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl-n-butyl ether, tetraethylene glycol di-n-butyl ether, tetraethylene glycol methyl-n-hexyl ether , tetraethylene glycol di-n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl ether Dipropylene glycol methyl-n-butyl ether, dipropylene 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 glycol di-n-butyl Ether, tetrapropylene glycol methyl-n-hexyl ether, tetrapropylene glycol di-n-butyl ether and other ether solvents; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, acetic acid Second butyl ester, n-amyl acetate, second amyl acetate, 3-methoxybutyl acetate, methyl amyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, acetic acid 2- (2-Butoxyethoxy)ethyl ester, benzyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, decyl acetate, methyl acetate, ethyl acetate, diethylene glycol Methyl ether, diethylene glycol monoethyl ether, dipropylene glycol methyl ether, dipropylene glycol diethyl ether, ethylene glycol diacetate, A Triethylene glycol acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate , n-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether Ester ester solvents such as ester, propylene glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone; acetonitrile, N-methylpyrrolidone, N-ethylpyrrolidone, N-propylpyrrolidone , N-butylpyrrolidone, N-hexyl pyrrolidone, N-cyclohexyl pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl Aprotic polar solvents such as hydrazine; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, second butanol, tert-butanol, n-pentanol, isoamyl alcohol, 2-methyl Butanol, second pentanol, third pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, second hexanol, 2- Ethyl butanol, second heptanol, n-octanol, 2-ethylhexanol, second octanol, n-nonanol, n-nonanol, second-undecanol, trimethylnonanol, second- Tetradecane, second-heptadecanol, phenol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-butanediol, diethylene glycol, two Alcohol solvent such as propylene glycol, triethylene glycol or tripropylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethyl Glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, triethylene glycol monoethyl ether, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, a glycol monoether solvent such as tripropylene glycol monomethyl ether; α-terpinene, α-terpineol, laurylene, allo-ocimene, limonene, dipentene, α-pinene, β-pinene, rosinol , terpene ketone, ocene, celery and other terpene solvents; water. These solvents may be used alone or in combination of two or more. When the n-type diffusion layer forming composition is formed, from the viewpoint of imparting flexibility to the substrate, α-terpineol, diethylene glycol mono-n-butyl ether, and diethylene glycol mono-acetate are preferred. N-butyl ether, as a more preferable solvent, α-terpineol and diethylene glycol mono-n-butyl ether can be mentioned.

The content ratio of the dispersion medium in the n-type diffusion layer forming composition is determined in consideration of coatability and donor concentration.

The viscosity of the n-type diffusion layer forming composition is preferably 10 mPa in view of imparting flexibility. Above s, 1000000mPa. s below.

The method for producing an n-type diffusion layer of the present invention includes a step of providing a composition for forming the n-type diffusion layer on a semiconductor substrate, and a step of subjecting the semiconductor substrate after the application to thermal diffusion treatment. Further, a method for producing a solar cell element according to the present invention includes the steps of: providing a composition for forming the n-type diffusion layer on a semiconductor substrate; and performing a thermal diffusion treatment on the semiconductor substrate after the application to form an n-type diffusion layer; And a step of forming an electrode on the formed n-type diffusion layer.

A method of manufacturing an n-type diffusion layer and a solar cell element of the present invention will be described with reference to FIG. Fig. 1 is a schematic cross-sectional view conceptually showing an example of a manufacturing procedure of a solar cell element of the present invention. In addition, in Fig. 1, 10 denotes a p-type semiconductor substrate, 12 denotes an n-type diffusion layer, 14 denotes a p ⁺ -type diffusion layer, 16 denotes an anti-reflection film, 18 denotes a surface electrode, and 20 denotes a back surface electrode (electrode layer). In the following drawings, the same components are denoted by the same reference numerals, and their description is omitted. In the following description, an example in which a tantalum substrate is used as a p-type semiconductor substrate will be described. However, in the present invention, the semiconductor substrate is not limited to a tantalum substrate.

In (1) of FIG. 1, an alkaline solution is applied to a tantalum substrate as a p-type semiconductor substrate 10 to remove a damaged layer, and a texture structure is obtained by etching.

Specifically, the damaged layer of the crucible surface generated when slicing from the ingot was removed using 20% by mass of caustic soda. Then, etching was carried out by using a mixed solution of 1% by mass of caustic soda and 10% by mass of isopropyl alcohol to form a texture structure (the description of the texture structure is omitted in the drawing). The solar cell element forms a texture structure on the light-receiving surface (surface) side, thereby promoting the light confinement effect and achieving high efficiency.

In (2) of FIG. 1, the n-type diffusion layer forming composition is applied to the surface of the p-type semiconductor substrate 10, that is, the surface on which the light-receiving surface is formed, and the n-type diffusion layer forming composition layer 11 is formed. In the present invention, the method of imparting is not limited, and examples thereof include a printing method, a spinning method, a brush coating method, a spray method, a doctor blade method, a roll coater method, and an inkjet method.

The amount of the n-type diffusion layer forming composition to be applied is not particularly limited. For example, the amount of the glass powder may be from 0.01 g/m ² to 100 g/m ² , preferably from 0.1 g/m ² to 10 g/m ² .

Further, depending on the composition of the n-type diffusion layer forming composition, a drying step for volatilizing the solvent contained in the composition after application may be required. In this case, it is dried for 1 minute to 10 minutes when using a hot plate at a temperature of about 80 ° C to 300 ° C, and dried for 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 in the present invention.

Further, when the manufacturing method of the present invention is used, the method of producing the p ⁺ -type diffusion layer (high-concentration electric field layer) 14 on the back surface is not limited to the method of converting the n-type diffusion layer into a p-type diffusion layer by aluminum. Any of the previously known methods can also be employed, and the options for the manufacturing method are expanded. Therefore, for example, the composition 13 containing an element of Group 13 such as B (boron) can be imparted to form the p ⁺ -type diffusion layer 14.

The composition 13 containing the element of Group 13 such as B (boron) may be, for example, a glass powder containing an acceptor element instead of a glass powder containing a donor element, and the same composition as that of the n-type diffusion layer. The p-type diffusion layer formed by the method forms a composition. The acceptor element may be an element of Group 13 and examples thereof include B (boron), Al (aluminum), and Ga (gallium). Further, the glass powder containing the acceptor element preferably contains at least one selected from the group consisting of B ₂ O ₃ , Al ₂ O ₃ and Ga ₂ O ₃ .

Further, the method of imparting the p-type diffusion layer forming composition to the back surface of the tantalum substrate is the same as the method of applying the n-type diffusion layer forming composition to the tantalum substrate as described above.

The p ⁺ -type diffusion layer 14 can be formed on the back surface by thermally diffusing the p-type diffusion layer forming composition applied to the back surface in the same manner as the thermal diffusion treatment of the n-type diffusion layer forming composition described later. Further, it is preferable that the thermal diffusion treatment of the p-type diffusion layer forming composition and the thermal diffusion treatment of the n-type diffusion layer forming composition are simultaneously performed.

Then, the p-type semiconductor substrate 10 on which the n-type diffusion layer forming composition layer 11 is formed is thermally diffused at a temperature equal to or higher than the melting point of the glass powder in the composition, for example, 600 to 1200 °C. By this thermal diffusion treatment, as shown in (3) of FIG. 1, the donor element is diffused into the semiconductor substrate to form the n-type diffusion layer 12. As the heat diffusion treatment, a known continuous furnace, a batch furnace, or the like can be applied. In addition, the furnace environment during the thermal diffusion treatment may be appropriately adjusted to air, oxygen, nitrogen, or the like.

The thermal diffusion treatment time can be appropriately selected in accordance with the content ratio of the donor element contained in the n-type diffusion layer forming composition. For example, it can be set to 1 minute to 60 minutes, more preferably 5 minutes to 30 minutes.

A glass layer (not shown) such as phosphoric acid glass is formed on the surface of the formed n-type diffusion layer 12. Therefore, the phosphoric acid glass is removed by etching. The etching can be carried out by any 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. When an etching method of immersing in an acid such as hydrofluoric acid is used, the immersion time is not particularly limited, and it can be usually 0.5 minutes to 30 minutes, preferably 1 minute to 10 minutes.

In the method of forming the n-type diffusion layer of the present invention shown in (2) of FIG. 1 and (3) of FIG. 1, the n-type diffusion layer 12 is formed at a desired portion, and unnecessary formation is not performed on the back surface or the side surface. N-type diffusion layer.

Therefore, in the previously widely used method of forming an n-type diffusion layer by a gas phase reaction method, a side etching step for removing an unnecessary n-type diffusion layer formed on the side is required, but the manufacturing method according to the present invention There is no need for a side etching step to simplify the steps. As described above, according to the manufacturing method of the present invention, a uniform n-type diffusion layer having a desired shape is formed at a desired portion in a short time.

Further, in the prior manufacturing method, it is necessary to convert an unnecessary n-type diffusion layer formed on the back surface into a p-type diffusion layer, and as the conversion method, the following method is employed: coating on the n-type diffusion layer on the back surface A paste of aluminum of a Group 13 element is calcined to diffuse aluminum to the n-type diffusion layer to convert the n-type diffusion layer into a p-type diffusion layer. In this method, in order to sufficiently convert the n-type diffusion layer into a p-type diffusion layer and further form a high-concentration electric field layer of the p ⁺ -type diffusion layer, a certain amount of aluminum is required, so it is necessary to form an aluminum layer. thick. However, since the coefficient of thermal expansion of aluminum is greatly different from the coefficient of thermal expansion of the crucible used as the substrate, a large internal stress is generated in the crucible substrate during the firing and cooling, which causes the warpage of the crucible substrate.

This internal stress causes damage to the grain boundary of the crystal and increases the power loss. Further, in the process of transferring the solar cell element in the module process or the connection to a copper wire called a tape automatic bonding (TAB) wire, the solar cell element is easily broken. In recent years, as the slicing technology has been improved, the thickness of the tantalum substrate is being thinned, and the solar cell element tends to be more easily broken.

However, according to the manufacturing method of the present invention, since an unnecessary n-type diffusion layer is not formed on the back surface, it is not necessary to perform conversion from the n-type diffusion layer toward the p-type diffusion layer without thickening the aluminum layer. As a result, generation or warpage of internal stress in the ruthenium substrate can be suppressed. As a result, an increase in power loss or breakage of the solar cell element can be suppressed.

Further, when the manufacturing method of the present invention is used, the method of producing the p ⁺ -type diffusion layer (high-concentration electric field layer) 14 on the back surface is not limited to the method of converting the n-type diffusion layer into a p-type diffusion layer by aluminum. Any method can also be used, and the options of the manufacturing method are expanded.

For example, a glass powder containing an acceptor element is used instead of the glass powder containing the donor element, and 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 tantalum substrate. (The surface opposite to the surface to which the n-type diffusion layer forming composition is applied) is subjected to a firing treatment to form a p ⁺ -type diffusion layer (high-concentration electric field layer) 14 on the back surface.

Further, as will be described later, the material for the back surface electrode 20 is not limited to aluminum of Group 13, and for example, Ag (silver) or Cu (copper) may be applied, and the thickness of the back surface electrode 20 may be formed thinner than the previous thickness. .

In (4) of FIG. 1, an anti-reflection film 16 is formed on the n-type diffusion layer 12. The anti-reflection film 16 is formed using a well-known technique. For example, when the anti-reflection film 16 is a tantalum nitride film, it is formed by a plasma chemical vapor deposition (CVD) method using a mixed gas of SiH ₄ and NH ₃ as a raw material. At this time, hydrogen diffuses in the crystal, does not participate in the orbital of the bonding of the deuterium atoms, that is, the dangling bonds are hydrogen-bonded, and the defects are passivated (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 (0.1 Torr) to 266.6 Pa (2 Torr), and the film forming temperature is 300 ° C to 550 ° C. It is formed under the condition that the frequency of discharge of the plasma is 100 kHz or more.

In (5) of Fig. 1, a metal paste for surface electrode coating is applied onto an antireflection film 16 having a surface (light-receiving surface) by a screen printing method, and dried to form a metal paste layer for a surface electrode. . The metal paste for surface electrodes contains (1) metal particles and (2) glass particles as essential components, and if necessary, (3) a resin binder and (4) other additives.

Then, a metal paste layer 19 for a back surface electrode is also formed on the p ⁺ -type diffusion layer 14 on the back surface. As described above, in the present invention, the material or formation method of the metal paste layer 19 for back surface electrodes is not particularly limited. For example, a paste for a back surface electrode containing a metal such as aluminum, silver or copper may be applied and dried to form a metal paste layer 19 for a back surface electrode. At this time, in order to connect the solar cell elements in the module process, a silver paste for silver electrode formation may be provided on a part of the back surface.

In (6) of Fig. 1, the electrode paste metal layer 17 is fired to form a solar cell element. When calcined in the range of 600 ° C to 900 ° C for several seconds to several minutes, the antireflection film 16 as an insulating film is melted on the surface side by the glass particles contained in the metal paste for the electrode, and the p-type semiconductor substrate 10 is further melted. A part of the surface is also melted, and 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 referred to as fire through. Further, on the back surface side, the back surface electrode of the back surface electrode metal paste layer 19 is similarly fired with a metal paste to form the back surface electrode 20.

The shape of the surface electrode 18 will be described with reference to FIGS. 2A and 2B. Further, in FIGS. 2A and 2B, 30 denotes a bus bar electrode, and 32 denotes a finger electrode. The surface electrode 18 includes a bus bar electrode 30 and a finger electrode 32 that intersects the bus bar electrode 30. 2A is a plan view of a solar cell element in which the surface electrode 18 is formed to include the bus bar electrode 30 and the finger electrode 32 crossing the bus bar electrode 30, and FIG. 2B is a part of FIG. 2A. Expand the perspective view of the representation.

Such a surface electrode 18 can be formed by, for example, 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, or the like. As is well known, the surface electrode 18 including the bus bar electrode 30 and the finger electrode 32 is generally used as an electrode on the light-receiving surface side, and a known method of forming the bus bar electrode and the finger electrode on the light-receiving surface side can be applied.

In the above description, a solar cell element in which an n-type diffusion layer is formed on the surface, a p ⁺ -type diffusion layer is formed on the back surface, and a surface electrode and a back surface electrode are provided on each layer has been described. However, the n-type of the present invention is used. When the diffusion layer forms a composition, a back contact type solar cell element can be produced.

The back contact type solar cell element is a solar cell element in which all of the electrodes are provided on the back surface to increase the area of the light receiving surface. In other words, in the back contact type solar cell element, both the n-type diffusion portion and the p ⁺ -type diffusion portion must be formed on the back surface to form a pn junction structure. Since the n-type diffusion layer forming composition of the present invention can form an n-type diffusion site at a specific portion, it can be preferably applied to the manufacture of a back contact type solar cell element.

In the present invention, the n-type diffusion layer forming composition is used in the production of the n-type diffusion layer, and the n-type diffusion layer in the case of manufacturing the solar cell element including the semiconductor substrate and the n-type diffusion layer and the electrode. The use of the composition is formed. As described above, by forming the composition using the n-type diffusion layer of the present invention, it is possible to obtain a uniform n-type diffusion layer in a desired shape in a specific region without forming an unnecessary n-type diffusion layer in a short time, and A solar cell element having such an n-type diffusion layer can be obtained without forming an unnecessary n-type diffusion layer.

[Example]

Hereinafter, examples of the invention will be more specifically described, but the invention is not limited by the examples. Further, as long as there is no special description, the reagents are all used in the chemicals. In addition, "%" means "% by mass" as long as there is no explanation in advance. Further, unless otherwise stated, "cm/s" indicates the "linear velocity" obtained by dividing the flow rate of the gas flowing into the furnace by the cross-sectional area of the electric furnace.

[Example 1]

P ₂ O ₅ -SiO ₂ -CaO-based glass having a substantially spherical shape, an average particle diameter of 4 μm, and a d90 of 15 μm (softening temperature of 700 ° C, P ₂ O ₅ : 50) using an automatic mortar mixing device %, SiO ₂ : 43%, CaO: 7%) 3 g of powder, 2.1 g of ethyl cellulose, and 24.9 g of terpineol were mixed and pasteified to prepare an n-type diffusion layer forming composition.

Further, the shape of the glass particles was observed and judged using a TM-1000 scanning electron microscope manufactured by Hitachi High-Technologies Co., Ltd. The average particle diameter of the glass and d90 were calculated using a LS 13 320 laser scattering diffraction particle size distribution measuring apparatus (measuring wavelength: 632 nm) manufactured by Beckman Coulter (Stock). The softening temperature of the glass is DTG-60H type differential heat manufactured by Shimadzu Corporation. The thermogravimetric simultaneous measurement device was determined by a differential heat (DTA) curve.

Next, the prepared paste was applied to the surface of the p-type ruthenium substrate by screen printing, and dried on a hot plate at 150 ° C for 5 minutes. Then, the ethyl cellulose was removed by holding it in an oven set at 450 ° C for 1.5 minutes. Then, in an atmosphere flow (0.9 cm/s) environment, the electrode was held in an electric furnace set at 950 ° C for 10 minutes, thereby performing thermal diffusion treatment, and thereafter, the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer. Then, the running water is cleaned. Thereafter, drying is carried out.

The sheet resistance of the surface coated with the side of the n-type diffusion layer forming composition was 60 Ω/□, and P (phosphorus) was diffused to form an n-type diffusion layer. Further, the deviation of the sheet resistance value in the applied surface was σ = 0.8, and a uniform n-type diffusion layer was formed. On the other hand, the sheet resistance of the back surface was 1,000,000 Ω/□ or more and could not be measured, and an n-type diffusion layer was not formed.

Further, the sheet resistance was a Loresta-EP MCP-T360 type low resistivity meter manufactured by Mitsubishi Chemical Co., Ltd., and was measured by a four-probe method at 25 °C.

Further, σ represents a standard deviation, which is calculated by dividing the sum of the squares of the deviations of the sheet resistance values at 25 points in the applied plane by the square root of the value obtained by dividing the number of the data.

[Example 2]

An n-type diffusion layer was formed in the same manner as in Example 1 except that the average particle diameter of the glass powder was 2 μm and d90 was 6.5 μm.

The sheet resistance of the surface coated with the side of the n-type diffusion layer forming composition was 33 Ω/□, and P (phosphorus) was diffused to form an n-type diffusion layer. Further, the deviation of the sheet resistance value in the applied surface was σ = 0.5, and a uniform n-type diffusion layer was formed. On the other hand, the sheet resistance of the back surface was 1,000,000 Ω/□ or more and could not be measured, and an n-type diffusion layer was not formed.

[Example 3]

An n-type diffusion layer was formed in the same manner as in Example 1 except that the average particle diameter of the glass powder was changed to 0.7 μm and d90 was set to 3.4 μm.

The sheet resistance of the surface coated with the side of the n-type diffusion layer forming composition was 25 Ω/□, and P (phosphorus) was diffused to form an n-type diffusion layer. Further, the deviation of the sheet resistance value in the applied surface was σ = 0.3, and a uniform n-type diffusion layer was formed. On the other hand, the sheet resistance of the back surface was 1,000,000 Ω/□ or more and could not be measured, and an n-type diffusion layer was not formed.

[Example 4]

P ₂ O ₅ -SiO ₂ -CaO-based glass having a particle shape of substantially spherical shape, an average particle diameter of 2 μm, and a d90 of 6.5 μm and having a softening temperature higher than that of Example 1 using an automatic mortar mixing device (softening temperature) 800 ° C, P ₂ O ₅ : 44%, SiO ₂ : 49%, CaO: 7%) powder 3 g, ethyl cellulose 2.1 g, and terpineol 24.9 g were mixed and pasteified to prepare n-type The diffusion layer forms a composition. Next, the prepared paste was applied to the surface of the p-type ruthenium substrate by screen printing, and dried on a hot plate at 150 ° C for 5 minutes. Then, in an atmosphere flow (0.9 cm/s) environment, heat diffusion treatment was performed by holding in an electric furnace set at 950 ° C for 10 minutes, and then the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer, and then Perform running water cleaning. Thereafter, drying is carried out.

The sheet resistance of the surface coated with the side of the n-type diffusion layer forming composition was 42 Ω/□, and P (phosphorus) was diffused to form an n-type diffusion layer. Further, the deviation of the sheet resistance value in the applied surface was σ = 0.5, and a uniform n-type diffusion layer was formed. On the other hand, the sheet resistance of the back surface was 1,000,000 Ω/□ or more and could not be measured, and an n-type diffusion layer was not 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 of the glass powder was 8 μm and d90 was 50 μm.

The sheet resistance of the surface coated with the side of the n-type diffusion layer forming composition was 120 Ω/□, and P (phosphorus) was diffused to form an n-type diffusion layer. However, the deviation (σ = 10.7) can be seen in the sheet resistance value in the plane, and is not uniform.

[Comparative Example 2]

An n-type diffusion layer was formed in the same manner as in Example 1 except that the average particle diameter of the glass powder was 30 μm and d90 was 110 μm.

The sheet resistance of the surface on the side where the n-type diffusion layer was formed on the composition was 300 Ω/□, and P (phosphorus) was diffused to form an n-type diffusion layer. However, the deviation (σ = 24.9) can be seen in the in-plane sheet resistance value, and is not uniform.

[Comparative Example 3]

P ₂ O ₅ -SnO-based glass having a particle shape of substantially spherical shape, an average particle diameter of 2 μm, and a d90 of 6.5 μm (softening temperature of 300 ° C, P ₂ O ₅ : 30%, using an automatic mortar mixing device) SnO: 70%) 3 g of powder, 2.1 g of ethyl cellulose, and 24.9 g of terpineol were mixed and pasteified to prepare an n-type diffusion layer forming composition.

Next, the prepared paste was applied to the surface of the p-type ruthenium substrate by screen printing into a fine line of 120 μm width, and dried on a hot plate at 150 ° C for 5 minutes. Then, under nitrogen flow (0.9 cm/s) In the environment, the thermal diffusion treatment was performed by holding in an electric furnace set at 950 ° C for 10 minutes, and thereafter, the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer, and then washed with running water. Thereafter, drying is carried out.

The sheet resistance of the portion in which the n-type diffusion layer forming composition was applied in a thin line shape was 120 Ω/□, and P (phosphorus) was diffused to form an n-type diffusion layer. Further, the width of the applied fine line pattern became 400 μm, and the molten glass was dripped, so that selective diffusion to a specific portion could not be achieved.

[Comparative Example 4]

Mixing 20 g of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) powder, 3 g of ethyl cellulose, and 7 g of 2-(2-butoxyethoxy)ethyl acetate using an automatic nipple mixing device and paste The n-type diffusion layer is formed into a composition.

Next, the prepared paste was applied to the surface of the p-type ruthenium substrate by screen printing, and dried on a hot plate at 150 ° C for 5 minutes. Then, the film was subjected to thermal diffusion treatment for 10 minutes in an electric furnace set at 1000 ° C, and thereafter, the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer, and then washed with water and dried.

The sheet resistance of the surface coated with the side of the n-type diffusion layer forming composition was 14 Ω/□, and P (phosphorus) was diffused to form an n-type diffusion layer. However, the sheet resistance of the back surface was 50 Ω/□, and an n-type diffusion layer was formed on the back surface.

[Comparative Example 5]

A solution was prepared by mixing 1 g of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) powder, 7 g of pure water, 0.7 g of polyvinyl alcohol, and 1.5 g of isopropyl alcohol using an automatic nipple mixing device to prepare an n-type. Diffusion layer composition.

Next, the prepared solution was applied onto the surface of a p-type ruthenium substrate by a spin coater (2000 rpm, 30 sec), and dried on a hot plate at 150 ° C for 5 minutes. Then, the film was subjected to thermal diffusion treatment for 10 minutes in an electric furnace set at 1000 ° C, and thereafter, the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer, and then washed with water and dried.

The sheet resistance of the surface coated with the side of the n-type diffusion layer forming composition was 10 Ω/□, and P (phosphorus) was diffused to form an n-type diffusion layer. However, the sheet resistance of the back surface was 100 Ω/□, and an n-type diffusion layer was formed on the back surface.

Japanese patent application filed on July 5, 2011 by reference The entire contents disclosed in 2011-149249 are incorporated in the present specification.

All the documents, patent applications, and technical specifications described in the specification are incorporated herein by reference to the same extent as the following, which is specifically and individually described by reference. The status of each document, patent application, and technical specifications.

10‧‧‧p type semiconductor substrate

11‧‧‧n type diffusion layer forming composition layer

12‧‧‧n type diffusion layer

13‧‧‧Composition

14‧‧‧p ⁺ diffusion layer

16‧‧‧Anti-reflective film

17‧‧‧Metal paste layer for surface electrodes

18‧‧‧ surface electrode

19‧‧‧Metal paste layer for back electrode

20‧‧‧Back electrode

Claims (6)

An n-type diffusion layer forming composition comprising: a glass powder containing a donor element and having a softening temperature of 500 ° C or more and 900 ° C or less and an average particle diameter of 5 μm or less; and a dispersing medium. The n-type diffusion layer forming composition according to claim 1, wherein the glass powder has a d90 of 20 μm or less. The n-type diffusion layer forming composition according to the first or second aspect of the invention, wherein the donor element is at least one selected from the group consisting of P (phosphorus) and Sb (antimony). The n-type diffusion layer forming composition according to any one of claims 1 to 3, wherein the glass powder containing the above-mentioned donor element comprises: selected from the group consisting of P ₂ O ₃ , P ₂ O ₅ and Sb At least one substance containing a donor element in the group consisting of ₂ O _{3 and} selected from the group consisting of SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, At least one glass component substance in a group consisting of PbO, CdO, SnO, ZrO ₂ and MoO ₃ . A method of producing an n-type diffusion layer, comprising: a step of imparting an n-type diffusion layer forming composition according to any one of claims 1 to 4 on a semiconductor substrate; The semiconductor substrate is subjected to a step of thermal diffusion treatment. A method of manufacturing a solar cell element, comprising: a step of applying a n-type diffusion layer forming composition according to any one of claims 1 to 4 on a semiconductor substrate; and applying the semiconductor after the imparting a step of forming a n-type diffusion layer by performing thermal diffusion treatment on the substrate; and forming an electrode on the n-type diffusion layer formed.