JP5176158B1 - N-type diffusion layer forming composition, method for producing n-type diffusion layer, and method for producing solar cell element - Google Patents

Abstract

The present invention provides an n-type diffusion layer forming composition containing a donor element, a glass powder 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 dispersion medium. .
[Selection figure] None

Description

  The present invention relates to a composition for forming an n-type diffusion layer of a solar cell element, a method for producing an n-type diffusion layer, and a method for producing a solar cell element. More specifically, the present invention relates to a specific region of silicon as a semiconductor substrate. The present invention relates to a technique that makes it possible to form a mold diffusion layer.

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

On the other hand, in the semiconductor manufacturing field, by applying a solution containing a phosphate such as phosphorus pentoxide (P ₂ O ₅ ) or ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) as a donor element-containing compound. A method for forming an n-type diffusion layer has been proposed (see, for example, JP-A-2002-75894). In addition, for forming a diffusion layer, 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 (for example, Japanese Patent No. 4073968). See the official gazette).

  However, in these methods, the donor element or a compound containing the same is scattered from the solution or paste as a diffusion source, so that phosphorus is formed on the side surface and the back surface during the formation of the diffusion layer as in the gas phase reaction method using the mixed gas. And an n-type diffusion layer is formed in addition to the applied portion. In general, the upper surface of a semiconductor substrate such as a silicon substrate used for a solar cell has a texture structure in which a height difference between a convex portion and a concave portion is about 5 μm. Since it is applied to the surface of such a texture structure, the n-type diffusion layer may be formed unevenly.

  Thus, in forming the n-type diffusion layer, in the gas phase reaction using phosphorus oxychloride, not only one side (usually the light-receiving surface or the surface) that originally requires the n-type diffusion layer, but also the other side ( An n-type diffusion layer is also formed on the non-light-receiving surface or back surface) and side surfaces. In addition, even in a method in which a solution containing a compound containing phosphorus or a paste is applied and thermally diffused, an n-type diffusion layer is formed in addition to the surface as in the gas phase reaction method. Therefore, in order to have a pn junction structure as an element, it is necessary to perform etching on the side surface and convert the n-type diffusion layer to the p-type diffusion layer on the back surface. In general, an aluminum paste which is a Group 13 element is applied to the back surface and fired to convert the n-type diffusion layer into a p-type diffusion layer. Further, in the application of the solution, phosphorus is not uniformly diffused, and a non-uniform n-type diffusion layer is formed, leading to a decrease in conversion efficiency of the entire solar cell. Further, in the conventionally known method of applying a paste containing a donor element such as phosphorus as a diffusion source, the compound having the donor element is volatilized and gas is diffused and diffused in a region other than the region where diffusion is required. In particular, it is difficult to form a diffusion layer in a specific region.

  The present invention has been made in view of the above-described conventional problems, and can be applied 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. An object is to provide an n-type diffusion layer forming composition capable of forming a uniform n-type diffusion layer in a short time, a method for producing an n-type diffusion layer, and a method for producing a solar cell element.

Means for solving the problems are as follows.
<1> An n-type diffusion layer forming composition comprising a donor element, a glass powder 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 dispersion medium.
<2> The n-type diffusion layer forming composition according to claim 1, wherein d90 of the glass powder is 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 P (phosphorus) and Sb (antimony).
<4> The glass powder containing the donor element 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, Containing at least one glass component material selected from the group consisting of Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ and MoO _3. <1>-<3> The n type diffused layer formation composition in any one of <3>.
<5> On the semiconductor substrate, a step of applying the n-type diffusion layer forming composition according to any one of <1> to <4>, a step of applying a thermal diffusion treatment to the semiconductor substrate after the application, 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 the semiconductor substrate, and applying a thermal diffusion treatment to the semiconductor substrate after the application, n The manufacturing method of the solar cell element which has the process of forming a type | mold diffused layer, and the process of forming an electrode on the formed said n-type diffused layer.
<7> Use of the n-type diffusion layer forming composition according to any one of <1> to <4> in the production of an n-type diffusion layer.
<8> Use of the n-type diffusion layer forming composition according to any one of <1> to <4> in the production of a solar cell element including a semiconductor substrate, an n-type diffusion layer, and an electrode.

  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 in a short time without forming an n-type diffusion layer in an unnecessary region. 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 can be provided.

It is sectional drawing which shows notionally an example of the manufacturing process of the solar cell element of this invention. FIG. 2A is a plan view of the solar cell element as seen from the surface. 2B is an enlarged perspective view showing a part of FIG. 2A.

First, the n-type diffusion layer forming composition of the present invention will be described, and then the n-type diffusion layer and 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, “to” indicates a range including the numerical values described before and after the values as a minimum value and a 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.

The n-type diffusion layer forming composition of the present invention contains at least a donor element, has a softening temperature of 500 ° C. or more and 900 ° C. or less, and an average particle size of 5 μm or less (hereinafter simply referred to as “glass powder”). And a dispersion medium, and may further contain other additives as necessary in consideration of suitability for application (applicability) of the composition.
Here, the n-type diffusion layer forming composition contains a donor element, contains a glass powder 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 is applied to a semiconductor substrate. A material that can form an n-type diffusion layer by thermally diffusing this donor element.
By using an n-type diffusion layer forming composition containing a donor element, a glass powder 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 the thermal diffusion treatment is increased. It does not become too low, and the glass powder melts in a short time. As a result, an n-type diffusion layer is formed at a desired site, and an unnecessary n-type diffusion layer is not formed on the back surface or side surface.

Therefore, if the composition for forming an n-type diffusion layer of the present invention is applied, the side etching step that is essential in the gas phase reaction method that has been widely employed is not required, and the process is simplified. In addition, the step of converting the n-type diffusion layer formed on the back surface into the p ⁺ -type diffusion layer is not necessary. Therefore, the method for forming the p ⁺ -type diffusion layer on the back surface and the material, shape, and thickness of the back electrode are not limited, and the choice of manufacturing method, material, and shape to be applied is widened. 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.

  In addition, the glass powder contained in the n type diffused layer formation composition of this invention fuse | melts by baking, and forms a glass layer on an n type diffused layer. However, a glass layer is formed on the n-type diffusion layer even in a conventional gas phase reaction method or a method of applying a phosphate-containing solution or paste, and thus the glass layer produced in the present invention is a conventional method. Similarly to the above, it can be removed by etching. Therefore, the n-type diffusion layer forming composition of the present invention does not generate unnecessary products and does not increase the number of steps as compared with the conventional method.

In addition, since the donor component in the glass powder is difficult to volatilize even during firing, it is suppressed that the n-type diffusion layer is formed not only on the surface but also on the back surface and side surfaces due to the generation of the volatilizing gas.
The reason for this is considered that the donor component is hard to volatilize because it is strongly bonded to other elements as constituent elements in the glass.

  Thus, since 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 site, the concentration of the n-type donor element (dopant) is high. A selective region can be formed. On the other hand, it is common to form a selective region having a high concentration of n-type donor element by a gas phase reaction method which is a general method of an n-type diffusion layer or a method using a phosphate-containing solution alone. It is difficult.

The glass powder containing the donor element according to the present invention 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), As (arsenic), and the like. From the viewpoints of safety, ease of vitrification, etc., P or Sb is preferred.

Examples of the donor element-containing material used 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 , and P ₂ O ₃ It is preferable to use at least one selected from the group consisting of 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. Furthermore, it is preferable to contain the glass component substance described below.
Examples of glass component materials include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ , WO ₃ , MoO ₃ , MnO, Examples include La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , ZrO ₂ , GeO ₂ , TeO _2, and Lu ₂ O _3. SiO ₂ , K ₂ O, Na ₂ It is preferable to use at least one selected from the group consisting of 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, from ZrO _2, and MoO ₃ It is more preferable to use at least one selected from the group that.

Specific examples of the glass powder containing a donor element include a system containing both the donor element-containing material and the glass component material, and a P ₂ O ₅ -SiO ₂ system (in order of donor element-containing material-glass component material). in described, the same applies _{hereinafter), P 2 O 5 -K 2} O _based, 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 _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., a system containing P ₂ O ₅ as a donor element-containing material, a system containing the above P ₂ O ₅ system moth containing _Sb 2 _{O 3} as a donor element-containing material in place of the _P 2 _{O 5} Scan powder and the like.
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 it has been illustrated composite glass containing two components _may be a glass powder containing 3 components or more substances as required, such as P ₂ O ₅ -SiO ₂ -CaO.

  The content ratio of the glass component substance in the glass powder is preferably set as appropriate in consideration of the melting temperature, the softening temperature, the glass transition temperature, and the chemical durability, and is generally 0.1% by mass to 95% by mass. It is preferable that it is 0.5 mass% or more and 90 mass% or less.

Specifically, the content ratio of SiO ₂ in the case of the glass powder containing SiO ₂ is preferably in the range of 10 to 90 mass%.

The softening temperature of glass powder needs to be 500 degreeC or more and 900 degrees C or less from a viewpoint of the diffusibility at the time of a diffusion process, and dripping. Moreover, it is preferable that it is 600 to 800 degreeC, and it is more preferable that it is 700 to 800 degreeC. When the softening temperature is less than 500 ° C., the viscosity of the glass becomes too low during the diffusion treatment and dripping occurs, so that an n-type diffusion layer may be formed in addition to the specific portion. On the other hand, when the temperature is higher than 900 ° C., the glass powder may not be melted and a uniform n-type diffusion layer may not be formed.
As long as the softening temperature of the glass powder is in the range of 500 ° C. or higher and 900 ° C. or lower, no dripping occurs as described above, so an n-type diffusion layer is formed in a desired shape in a specific region after the diffusion treatment. It becomes possible to do. 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, and a scale shape. The n-type diffusion layer forming composition has a coating property (applicability) and uniform diffusibility. From this point, it is desirable that the shape is substantially spherical, flat or plate-like.

The average particle diameter of the glass powder is required to be 5 μm or less. Moreover, it is preferable that they are 0.1 micrometer-5 micrometers, and it is more preferable that they are 0.5 micrometer-4 micrometers.
By making the glass powder have an average particle diameter of 5 μm or less, even when a glass powder having a softening temperature in the above range is used, it is melted in a short time and a smooth glass layer is easily obtained. Therefore, a uniform n-type diffusion layer can be formed by setting the average particle diameter of the glass powder to 5 μm or less.

A uniform n-type diffusion layer can be confirmed, for example, as variations in sheet resistance (standard deviation: σ) in the n-type diffusion layer surface obtained by coating on a semiconductor substrate. For example, when the variation (σ) in the sheet resistance value is 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, as the sheet resistance, one measured at 25 ° C. by a four-probe method using a Loresta-EP MCP-T360 type low resistivity meter manufactured by Mitsubishi Chemical Corporation is adopted.
Further, σ is obtained by calculating the square root of the sum of the squares of the deviations of the sheet resistance values of 25 points obtained by the above-described measurement method for the coated surface by the number of data.

In general, the upper surface of a semiconductor substrate used in a solar cell has a texture structure in which the height difference between the convex portion and the concave portion is about 5 μm. For this reason, by setting the average particle diameter of the glass powder to 5 μm or less, followability to the surface of the recess is improved, so that uneven diffusion can be reduced.
Here, unless otherwise specified in the present specification, the average particle diameter of glass represents a volume average particle diameter, and can be measured by a laser scattering diffraction method particle size distribution analyzer (manufactured by Beckman Coulter, Inc.) or the like.

  As for d90 of the glass powder used for this invention, 20 micrometers or less are preferable. D90 is more preferably 15 μm or less, and further preferably 10 μm or less. Here, d90 refers to the particle diameter at which 90% of the total particle diameter is accumulated sequentially from the particle having the smallest particle diameter when a volume distribution accumulation curve of particle diameter is drawn. The volume distribution integrated curve can be measured in the same manner as the average particle diameter, and can be measured by a laser scattering diffraction particle size distribution measuring apparatus (manufactured by Beckman Coulter, Inc.).

  If d90 of the glass powder is 20 μm or less, after applying the n-type diffusion layer forming composition to the upper surface of the semiconductor substrate, the generation of large pores due to coarse particles is suppressed, and the distribution of donor elements is made more uniform. There is a tendency to be able to.

  In the glass powder in this invention, the softening temperature of glass powder is 500 to 900 degreeC, and an average particle diameter needs to be 5 micrometers or less. Further, the glass softening temperature is preferably 600 ° C. to 800 ° C., the average particle size is preferably 0.1 μm to 5 μm, the glass softening temperature is 700 ° C. to 800 ° C., and the average particle size is 0.5 μm. More preferably, it is ˜4 μm.

  Moreover, in the said glass powder, it is preferable that the softening temperature of glass powder is 500 to 900 degreeC, an average particle diameter is 5 micrometers or less, d90 is 20 micrometers or less, and the softening temperature of glass is 600 to 800 degreeC. The average particle size is 0.1 μm to 5 μm, d90 is more preferably 15 μm or less, the glass softening temperature is 700 ° C. to 800 ° C., and the average particle size is 0.5 μm to 4 μm. It is even more preferable that d90 is 10 μm or less.

In the glass powder, the glass softening temperature is 600 ° C. to 800 ° C., the average particle diameter is 0.1 μm to 5 μm, d90 is 15 μm or less, and the glass powder containing the donor element is P _2. At least one donor element-containing material selected from the group consisting of O ₃ , P ₂ O ₅ and Sb ₂ O ₃ , and SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, It is more preferable to contain at least one glass component material selected from the group consisting of MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ and MoO ₃ , and the softening temperature of the glass is 700 ° C. to 800 ° C. a ° C., an average particle diameter of 0.5Myuemu～4myuemu, d90 is not more 10μm or less, a glass powder containing the donor _{element, P 2 O 3, P 2} O 5 and S At least one donor element-containing material selected from the group consisting of _{2 O 3, SiO 2, K} 2 O, Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO It is even more preferable to contain at least one glass component substance selected from the group consisting of SnO, ZrO ₂ and MoO ₃ .

The glass powder containing a donor element is produced by the following procedure.
First, raw materials, for example, the donor element-containing material and the 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 substance and the glass component substance are heated at a temperature corresponding to the glass composition in an electric furnace to obtain a melt. At this time, it is desirable to stir the melt uniformly.
Subsequently, the obtained melt is poured onto a zirconia substrate, a carbon substrate or the like to vitrify the melt.
Finally, the glass is crushed into 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 the suitability for application (coating property), the 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 and 90% by mass or less, More preferably, it is 1.5 mass% or more and 85 mass% or less, and 2 mass% or more and 80 mass% or less are especially preferable.

Next, the dispersion medium will be described.
The dispersion medium is 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 employed as the dispersion medium.

  Examples of the binder include polyvinyl alcohol, polyacrylamide resin, polyvinyl amide resin, polyvinyl pyrrolidone, polyethylene oxide resin, polysulfonic acid, acrylamide alkyl sulfonic acid, cellulose ether resin, cellulose derivative, carboxymethyl cellulose, hydroxyethyl cellulose, ethyl cellulose, gelatin, starch And starch derivatives, sodium alginate and sodium alginate derivatives, xanthan and xanthan derivatives, gua and gua derivatives, scleroglucan and scleroglucan derivatives, tragacanth and tragacanth derivatives, dextrin and dextrin derivatives, (meth) acrylic acid resin, (meth) Acrylic ester resin (eg, alkyl (meth) acrylate resin, dimethyl) Aminoethyl (meth) acrylate resin, etc.), butadiene resins, styrene resins, and copolymers thereof. In addition, a siloxane resin can be appropriately selected. These are used singly or in combination of two or more.

  The molecular weight of the binder is not particularly limited, and it is desirable to adjust appropriately in view of the desired viscosity of the composition.

  Examples of the solvent 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, Ketone solvents such as diethyl ketone, 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 Cold di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di- n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl-n-butyl ether, triethylene glycol di-n-butyl ether, triethylene Glico Methyl-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetradiethylene glycol methyl ethyl ether, tetraethylene glycol methyl-n-butyl ether, diethylene 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 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, tetradipropylene glycol methyl ethyl ether, Tetrapropylene glycol methyl-n-butyl ether, dipropylene glycol Ether solvents such as alkyl di-n-butyl ether, tetrapropylene glycol methyl n-hexyl ether, tetrapropylene 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-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate , Benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, acetic acid diethylene glycol methyl ether, acetic acid diethylene glycol monoethyl ether, acetic acid dipropylene glycol methyl ether, acetic acid diacetate Lopylene glycol ethyl ether, glycol diacetate, methoxytriglycol acetate, ethyl propionate, n-butyl propionate, i-amyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, lactate n -Butyl, 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 Ester solvents such as propyl ether acetate, γ-butyrolactone, γ-valerolactone; acetonitrile, N-methylpyrrolidinone, -Aprotic polar solvents such as ethylpyrrolidinone, N-propylpyrrolidinone, 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-undecyl alcohol, trimethylnonyl alcohol, s-tetradecyl alcohol, s-heptadecyl alcohol, phenol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propylene glycol, 1 , 3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and other alcohol solvents; 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- -Glycol monoether solvents such as hexyl ether, ethoxytriglycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether; α-terpinene , Terpene solvents such as α-terpineol, myrcene, alloocimene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, ocimene, and ferrandolene; water. These are used singly or in combination of two or more. In the case of an n-type diffusion layer forming composition, α-terpineol, diethylene glycol mono-n-butyl ether, and diethylene glycol mono-n-butyl ether are preferred from the viewpoint of suitability for application to the substrate, and α-terpineol, diethylene glycol mono-n- Butyl ether is mentioned as 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 and donor concentration.
The viscosity of the n-type diffusion layer forming composition is more preferably 10 mPa · s or more and 1000000 mPa · s or less in consideration of applicability.

  The manufacturing method of the n type diffused layer of this invention has the process of providing the said n type diffused layer formation composition on a semiconductor substrate, and the process of giving a thermal-diffusion process to the semiconductor substrate after the said provision. Moreover, the manufacturing method for the solar cell element of the present invention includes a step of applying the n-type diffusion layer forming composition on a semiconductor substrate, and applying a thermal diffusion treatment to the semiconductor substrate after the application, thereby performing n-type diffusion. Forming a layer, and forming an electrode on the formed n-type diffusion layer.

The manufacturing method of the n type diffused layer and solar cell element of this invention is demonstrated referring FIG. FIG. 1 is a schematic cross-sectional view conceptually showing an example of the manufacturing process of the solar cell element of the present invention. 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 using a silicon substrate as a p-type semiconductor substrate will be described. However, in the present invention, the semiconductor substrate is not limited to a silicon substrate.

In FIG. 1A, an alkaline solution is applied to a silicon substrate which is a p-type semiconductor substrate 10 to remove a damaged layer, and a texture structure is obtained by etching.
Specifically, the damaged layer on the 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. 1 (2), the n-type diffusion layer forming composition layer 11 is formed by applying the n-type diffusion layer forming composition to the surface of the p-type semiconductor substrate 10, that is, the surface serving as the light receiving surface. In the present invention, the application method is not limited, and examples thereof include a printing method, a spin method, a brush coating, a spray method, a doctor blade method, a roll coater method, and an ink jet method.
Is not particularly limited as application amount of the n-type diffusion layer forming composition, for example, be a 0.01g ^{/ m 2} ~100g ^/ m 2 as a glass powder content, 0.1 g ^/ m 2 to 10 g / M ² is preferable.

  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 1 minute to 10 minutes when a hot plate is used, and about 10 minutes to 30 minutes when a dryer or the like is used. The 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 manufacturing method of the p ⁺ -type diffusion layer (high concentration electric field layer) 14 on the back surface is limited to a method by conversion from an n-type diffusion layer to a p-type diffusion layer with aluminum. Therefore, 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) can be applied to form the p ⁺ -type diffusion layer 14.
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 same as the composition for forming an n-type diffusion layer. A p-type diffusion layer forming composition constituted as described above can be given. The acceptor element may be an element belonging to Group 13, 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 p ⁺ -type diffusion layer 14 can be formed on the back surface by subjecting the p-type diffusion layer forming composition applied to the back surface to a thermal diffusion treatment similar to the thermal diffusion treatment in the n-type diffusion layer forming composition described later. it can. 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 thermal diffusion treatment at a temperature equal to or higher than the melting point of the glass powder in the 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 of the donor element contained in the n-type diffusion layer forming composition. For example, it may be 1 minute to 60 minutes, and more 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 in an acid such as hydrofluoric acid and a method of immersing in an alkali such as caustic soda can be applied. In the case of using an etching method immersed in an acid such as hydrofluoric acid, the immersion time is not particularly limited, and can be generally 0.5 minutes to 30 minutes, preferably 1 minute to 10 minutes.

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

Further, in the conventional manufacturing method, it is necessary to convert an unnecessary n-type diffusion layer formed on the back surface into a p-type diffusion layer. As this conversion method, a group 13 element is added to the n-type diffusion layer on the back surface. A method is adopted in which an aluminum paste is applied and baked to diffuse aluminum into the n-type diffusion layer and convert it into a p-type diffusion layer. In this method, conversion to the p-type diffusion layer is sufficient, and in order to form a high-concentration electric field layer of the p ⁺ -type diffusion layer, a certain amount of aluminum is required. There was a need to form. However, since the thermal expansion coefficient of aluminum is significantly different from that of silicon used as a substrate, a large internal stress is generated in the silicon substrate during the firing and cooling process, causing warpage of the silicon substrate. .
This internal stress has a problem that the crystal grain boundary is damaged and the power loss increases. Further, the warpage easily damages the solar cell element in the transportation of the solar cell element in the module process and the connection with a copper wire called a tab wire. 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 invention, since an unnecessary n-type diffusion layer is not formed on the back surface, there is no need to perform conversion from the n-type diffusion layer to the p-type diffusion layer, and the necessity of thickening the aluminum layer is eliminated. . As a result, generation of internal stress and warpage in the silicon substrate can be suppressed. As a result, it is possible to suppress an increase in power loss and damage to the solar cell element.

Further, when the manufacturing method of the present invention is used, the manufacturing method of the p ⁺ -type diffusion layer (high concentration electric field layer) 14 on the back surface is limited to a method by conversion from an n-type diffusion layer to a p-type diffusion layer with aluminum. Any method can be adopted without any problem, and the choice of manufacturing method is expanded.
For example, 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 formed on the back surface (n The p ⁺ -type diffusion layer (high-concentration electric field layer) 14 is preferably formed on the back surface by applying to a surface opposite to the surface to which the mold diffusion layer-forming composition is applied and baking treatment.
As will be described later, the material used for the back electrode 20 is not limited to Group 13 aluminum. For example, Ag (silver) or Cu (copper) can be applied, and the thickness of the back electrode 20 is also conventional. It becomes possible to form thinner.

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 orbits that do not contribute to the bonding of silicon atoms, that is, dangling bonds and hydrogen are combined to inactivate defects (hydrogen passivation).
More specifically, the mixed gas flow rate ratio NH ₃ / SiH ₄ is 0.05 to 1.0, the reaction chamber pressure is 13.3 Pa (0.1 Torr) to 266.6 Pa (2 Torr), It is formed under conditions where the temperature is 300 ° C. to 550 ° C. and the frequency for plasma discharge is 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, a back electrode metal paste layer 19 is also formed on the p ⁺ -type diffusion layer 14 on the back surface. As described above, in the present invention, the material and forming method of the back electrode metal paste layer 19 are not particularly limited. For example, the back electrode metal paste layer 19 including a metal such as aluminum, silver or copper may be applied and dried to form the back electrode metal paste layer 19. At this time, a silver paste for forming a silver electrode may be partially provided on the back surface for connection between solar cell elements in the module process.

  In FIG. 1 (6), the electrode metal paste layer 17 is baked to complete the solar cell element. When fired in the range of 600 ° C. to 900 ° C. for several seconds to several minutes, the antireflection film 16 that is an insulating film is melted by the glass particles contained in the electrode metal paste on the surface side, and the surface of the p-type semiconductor substrate 10 is partially 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. 2A is a plan view of a solar cell element in which the surface electrode 18 includes a bus bar electrode 30 and finger electrodes 32 intersecting with the bus bar electrode 30 as viewed from the surface. FIG. 2B is a plan view of FIG. It is a perspective view which expands and shows a part of.

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

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

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

  Examples of the present invention will be described more specifically below, but the present invention is not limited to these examples. Unless otherwise stated, all chemicals used reagents. “%” 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 —CaO glass having a substantially spherical particle shape, an average particle diameter of 4 μm, and a d90 of 15 μm (softening temperature 700 ° C., P ₂ O ₅ : 50%, SiO ₂ : 43%, (CaO: 7%) 3 g of powder, 2.1 g of ethyl cellulose, and 24.9 g of terpineol were mixed using an automatic mortar kneader to make a paste, thereby preparing an n-type diffusion layer forming composition.

  The glass particle shape was determined by observing with a TM-1000 scanning electron microscope manufactured by Hitachi High-Technologies Corporation. The average particle diameter and d90 of the glass were calculated using a LS 13 320 type laser scattering diffraction particle size distribution analyzer (measurement wavelength: 632 nm) manufactured by Beckman Coulter, Inc. The softening temperature of the glass was obtained from a differential heat (DTA) curve using a DTG-60H type differential heat / thermogravimetric simultaneous measuring device manufactured by Shimadzu Corporation.

  Next, the prepared paste was applied to the surface of the p-type silicon substrate by screen printing and dried on a hot plate at 150 ° C. for 5 minutes. Next, it was kept in an oven set at 450 ° C. for 1.5 minutes to release ethyl cellulose. Subsequently, the substrate is immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer by performing thermal diffusion treatment by holding it in an electric furnace set at 950 ° C. for 10 minutes in an air flow (0.9 cm / s) atmosphere. 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 60Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. Further, the variation of the sheet resistance value in the coated surface was σ = 0.8, and a uniform 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 the four-probe method using a Loresta-EP MCP-T360 type low resistivity meter manufactured by Mitsubishi Chemical Corporation.
Further, σ represents a standard deviation, and was calculated by a square root of a sum of squares of deviations of 25 sheet resistance values in the coated surface divided by the number of 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 on which the n-type diffusion layer forming composition was applied was 33Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. In addition, the variation in the sheet resistance value in the coated surface was σ = 0.5, and a uniform 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.

[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 0.7 μm and d90 was 3.4 μm.
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 25Ω / □, and P (phosphorus) diffused to form an n-type diffusion layer. Further, the variation of the sheet resistance value in the coated surface was σ = 0.3, and a uniform 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.

[Example 4]
P ₂ O ₅ —SiO ₂ —CaO-based glass (softening temperature 800 ° C., P ₂₎ having a substantially spherical particle shape, an average particle diameter of 2 μm, and a d90 of 6.5 μm and a softening temperature higher than that of Example 1. (O ₅ : 44%, SiO ₂ : 49%, CaO: 7%) 3 g of powder, 2.1 g of ethyl cellulose, and 24.9 g of terpineol were mixed and pasted using an automatic mortar kneader, and n-type A diffusion layer forming composition was prepared. Next, the prepared paste was applied to the surface of the p-type silicon substrate by screen printing and dried on a hot plate at 150 ° C. for 5 minutes. Subsequently, in an air flow (0.9 cm / s) atmosphere, heat diffusion treatment is performed for 10 minutes in an electric furnace set at 950 ° C., and then the substrate is immersed in hydrofluoric acid for 5 minutes to remove the glass layer. , 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 42 Ω / □, and P (phosphorus) diffused to form an n-type diffusion layer. In addition, the variation in the sheet resistance value in the coated surface was σ = 0.5, and a uniform 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 no 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 of the glass powder was 8 μm and d90 was 50 μm.
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 120 Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. However, the in-plane sheet resistance value was uneven (σ = 10.7) and was 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 which the n-type diffusion layer forming composition was applied was 300Ω / □, P (phosphorus) diffused, and an n-type diffusion layer was formed. However, there was variation in the sheet resistance value in the plane (σ = 24.9), which was uneven.

[Comparative Example 3]
3 g P ₂ O ₅ —SnO glass (softening temperature 300 ° C., P ₂ O ₅ : 30%, SnO: 70%) powder having a substantially spherical particle shape, an average particle diameter of 2 μm, and a d90 of 6.5 μm And 2.1 g of ethyl cellulose and 24.9 g of terpineol were mixed using an automatic mortar kneader to make a paste, thereby preparing an n-type diffusion layer forming composition.
Next, the prepared paste was applied to the surface of the p-type silicon substrate by screen printing in the form of a fine line having a width of 120 μm and dried on a hot plate at 150 ° C. for 5 minutes. Subsequently, in a nitrogen flow (0.9 cm / s) atmosphere, the substrate is immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer by performing thermal diffusion treatment by holding in an electric furnace set at 950 ° C. for 10 minutes. , Washed with running water. Thereafter, drying was performed.

  The sheet resistance of the portion where the composition for forming an n-type diffusion layer was applied in a thin line was 120Ω / □, P (phosphorus) was diffused, and an n-type diffusion layer was formed. Moreover, the width | variety of the apply | coated thin line-shaped pattern became 400 micrometers, and since the molten glass was dripping, the selective diffusion to the specific part was not able to be performed.

[Comparative Example 4]
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 were mixed using an automatic mortar kneader to make a paste, and n-type A diffusion layer composition was prepared.
Next, the prepared paste was applied to the surface of the p-type silicon substrate by screen printing and dried on a hot plate at 150 ° C. for 5 minutes. Subsequently, the substrate was immersed in hydrofluoric acid for 5 minutes, washed with running water, and dried to remove the glass layer by holding it for 10 minutes in an electric furnace set at 1000 ° C. for 10 minutes.

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

[Comparative Example 5]
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 are mixed using an automatic mortar kneader to prepare a solution. And an n-type diffusion layer composition was prepared.
Next, the prepared solution was applied to the surface of the p-type silicon substrate by a spin coater (2000 rpm, 30 sec) and dried on a hot plate at 150 ° C. for 5 minutes. Subsequently, the substrate was immersed in hydrofluoric acid for 5 minutes, washed with running water, and dried to remove the glass layer by holding it for 10 minutes in an electric furnace set at 1000 ° C. for 10 minutes.

  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. However, the sheet resistance on the back surface was 100Ω / □, and an n-type diffusion layer was also formed on the back surface.

The disclosure of Japanese Patent Application No. 2011-149249 filed on July 5, 2011 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference, Incorporated herein by reference.

Claims (6)

  An n-type diffusion layer forming composition containing a donor element, a glass powder 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 dispersion medium.   The n-type diffusion layer forming composition according to claim 1, wherein d90 of the glass powder is 20 μm or less.   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). The glass powder containing the donor element 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 , and SiO ₂ , K ₂ O, Na ₂ O. And 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 claims 1 to 3. Applying the n-type diffusion layer forming composition according to any one of claims 1 to 4 on a semiconductor substrate;
A step of applying a thermal diffusion treatment to the semiconductor substrate after the application;
The manufacturing method of the n type diffused layer which has this. 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 to form an n-type diffusion layer;
Forming an electrode on the formed n-type diffusion layer;
The manufacturing method of the solar cell element which has this.