JP6077907B2 - Diffusion agent composition and method for forming impurity diffusion layer - Google Patents

Description

  The present invention relates to a diffusing agent composition for forming an impurity diffusion layer in a semiconductor substrate and a method for forming the impurity diffusion layer.

  Conventionally, in the manufacture of solar cells, when an N-type impurity diffusion layer is formed in a semiconductor substrate, for example, a diffusing agent containing an N-type impurity diffusing component is changed from the diffusing agent applied to the surface of the semiconductor substrate to the N-type. The N-type impurity diffusion layer was formed by diffusing the impurity diffusion component. Specifically, first, a thermal oxide film is formed on the surface of the semiconductor substrate, and then a resist having a predetermined pattern is stacked on the thermal oxide film by photolithography, and the resist is used as a mask with an acid or an alkali. The portion of the thermal oxide film that is not masked is etched, and the resist is removed to form a mask of the thermal oxide film. Then, a diffusing agent containing an N-type impurity diffusing component is applied to form a diffusion composition film in a portion where the mask is open. The portion is diffused at a high temperature to form an N-type impurity diffusion layer.

JP2012-9627

  In conventional coating (printing) type diffusing agent compositions, an impurity diffusing component, a binder, and a diluting solvent are usually present independently. Conventionally used impurity diffusion components are relatively low molecules, and therefore easily sublimate due to heat. Therefore, in the thermal diffusion process, impurity diffusion components are scattered in the non-coated (printed) portion, and extra impurity diffusion occurs. In particular, since high-efficiency solar cells in recent years often employ a back contact type, there is an increasing need to avoid contamination between the P layer and the N layer as much as possible, and impurity diffusion components are not applied by heat treatment. Technology that suppresses scattering in the (printing) part is important.

  The present invention has been made in view of such problems, and its purpose is to provide an impurity diffusion component contained in the diffusing agent composition when the diffusing agent composition is formed on the substrate by coating or printing and then heat treatment is performed. It exists in provision of the technique which can suppress scattering from an application part to a non-application part.

［式中、Ｒはそれぞれ独立に有機基または水酸基である。］ One embodiment of the present invention is a diffusing agent composition used for forming an impurity diffusion component in a semiconductor substrate, in which an —O—Si—O— bond and a —P (═O) n— bond [n is 0 or 1],
The —O—Si—O— bond is a bond having 2 to 3 functional groups represented by the following formula.

[Wherein, each R is independently an organic group or a hydroxyl group. ]

［式中、Ｘはそれぞれ独立に前記Ｒまたは架橋酸素であり（ただし、少なくとも１つのＸは前記Ｒである）、Ｙはそれぞれ独立に前記Ｒ、架橋酸素であり、ｎは０または１である。］ The diffusing agent composition of the above aspect may have a skeleton represented by the following formula.

[Wherein, X is independently R or bridging oxygen (wherein at least one X is R), Y is independently R or bridging oxygen, and n is 0 or 1] . ]

  Another embodiment of the present invention is a method for forming an impurity diffusion layer. The impurity diffusion layer forming method includes a pattern forming step of applying a diffusing agent composition according to any one of the above-described aspects to a semiconductor substrate to form a pattern, and phosphorus atoms in the diffusing agent composition are transferred to the semiconductor substrate. And a diffusion step of diffusing into the substrate.

  Yet another embodiment of the present invention is a solar cell. The solar cell includes a semiconductor substrate and an impurity diffusion layer formed by the impurity diffusion layer formation method of the above-described embodiment.

  ADVANTAGE OF THE INVENTION According to this invention, when heat processing is implemented after apply | coating a diffusing agent composition to a board | substrate, it can suppress that an impurity diffusion component disperses from an application part to a non-application part.

1A to 1D are process cross-sectional views for explaining a method for manufacturing a solar cell including a method for forming an impurity diffusion layer according to an embodiment. 2A to 2D are process cross-sectional views for explaining a method for manufacturing a solar cell including a method for forming an impurity diffusion layer according to an embodiment.

  The diffusing agent composition according to the embodiment is suitably used for forming an impurity diffusing component in a semiconductor substrate. A solar cell is suitable for the use of the semiconductor substrate.

上式中、Ｒはそれぞれ独立に有機基または水酸基である。有機基としては、たとえば、置換基を有していても良いアルキル基、アルコキシ基、アリール基、アルケニル基が挙げられる。 The diffusing agent composition according to the embodiment has a —O—Si—O— bond and a —P (═O) n— bond [n is 0 or 1], and the above —O—Si—O— bond. Is a bond having 2 to 3 functional groups represented by the following formula. That is, in the diffusing agent composition according to the embodiment, the impurity diffusing component also has a function as a binder component for forming a film or a film pattern, and can improve diffusion controllability. Moreover, by having 2-3 functional groups, the stability of the impurity diffusion component is improved even when the impurity diffusion component is provided with a function as a binder component (high molecular weight). Hereinafter, the compound has —O—Si—O— bond and —P (═O) n— bond [n is 0 or 1], and the —O—Si—O— bond is represented by the formula 2 A compound that is a bond having a trifunctional group will be described as an impurity diffusion component (A) (hereinafter also referred to as component (A)).

In the above formula, each R is independently an organic group or a hydroxyl group. As an organic group, the alkyl group, alkoxy group, aryl group, and alkenyl group which may have a substituent are mentioned, for example.

The alkyl group may be linear, branched or cyclic.
The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms. Specifically, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decanyl group, undecyl group, dodecyl group, tridecyl group, isotridecyl group, tetradecyl group Group, pentadecyl group, hexadecyl group, isohexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, heicosyl group, docosyl group and the like.

  The branched alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 15 carbon atoms, and most preferably 3 to 10 carbon atoms. Specifically, for example, 1-methylethyl group, 1-methylpropyl group, 2-methylpropyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group, Examples include 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group and the like.

  The cyclic alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 12 carbon atoms, and may be polycyclic or monocyclic. The monocyclic alkyl group is a group obtained by removing one or more hydrogen atoms from a monocycloalkane, specifically, a group obtained by removing one or more hydrogen atoms from cyclobutane, cyclopentane, cyclohexane or the like. Is mentioned. The polycyclic cyclic alkyl group is a group obtained by removing one or more hydrogen atoms from a polycycloalkane, specifically one or more from adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, etc. And a group in which a hydrogen atom is removed.

  As an alkoxy group, it is preferable that it is C1-C20, and the part of the alkyl group in an alkoxy group may be linear, branched or cyclic, and the same thing as the said alkyl group is mentioned.

  The aryl group is an aromatic hydrocarbon group, preferably having 6 to 20 carbon atoms, for example, a group in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring such as benzene, biphenyl, fluorene, naphthalene, anthracene, phenanthrene; And a group obtained by removing one or more hydrogen atoms from an aromatic heterocycle in which a part of carbon atoms constituting the aromatic hydrocarbon ring is substituted with a heteroatom. Examples of the hetero atom in the aromatic heterocyclic ring include an oxygen atom, a sulfur atom, and a nitrogen atom.

The alkenyl group may be linear or branched, and preferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms. Examples of the linear alkenyl group include a vinyl group, a propenyl group (allyl group), and a butynyl group. Examples of the branched alkenyl group include a 1-methylpropenyl group and a 2-methylpropenyl group.
The alkyl group, aryl group, and alkenyl group each may have a substituent. Examples of the substituent include an alkyl group having 1 to 10 carbon atoms or an alkoxy group, an aryl group having 6 to 20 carbon atoms, and a carbon number. Examples thereof include 2 to 5 alkenyl groups, acryloyl groups, methacryloyl groups, acryloyloxy groups, methacryloyloxy groups, halogen atoms, halogenated alkyl groups having 1 to 10 carbon atoms, hydroxyl groups, carbonyl groups, nitro groups and amino groups.

  The -O-Si-O- bond in the diffusing agent composition according to the embodiment is preferably a bond having a bifunctional group. By having a bifunctional group, the stability of the component (A) is improved, and an increase in molecular weight over time can be suppressed.

  In the —P (═O) n— bond, n is preferably 1. Although it is a compound having a phosphoric acid skeleton as used for the reaction with a bifunctional or trifunctional chlorosilane compound or a silane compound in the production method described later, the reaction proceeds more easily than a compound having a phosphorous acid skeleton. It is because it is considered.

上式中、Ｘはそれぞれ独立に前記Ｒまたは架橋酸素であり（ただし、少なくとも１つのＸは上述したＲである）、Ｙはそれぞれ独立に上述したＲ、架橋酸素であり、ｎは０または１である。 As a skeleton containing an —O—Si—O— bond and a —P (═O) n— bond in the impurity diffusion component (A) (hereinafter sometimes referred to as an Si—O—P skeleton), The skeleton represented is mentioned.

In the above formula, each X is independently R or bridging oxygen (wherein at least one X is R described above), Y is each independently R described above, bridging oxygen, and n is 0 or 1 It is.

  Regarding X in the above formula, at least one X is R described above. The impurity diffusion component (A) preferably has a skeleton in which both X are R, and more preferably 50 to 100 mol% of the entire impurity diffusion component (A). The higher the ratio of the skeleton in which both X is R to the whole (A), the higher the moisture resistance and the more stable the impurity diffusion component (A).

350-5000 are preferable, as for the weight average molecular weight of the impurity diffusion component (A) in the diffusing agent composition which concerns on embodiment, 350-3000 are more preferable, and 400-2000 are more preferable. When the weight average molecular weight of the diffusing agent composition falls within the above range, diffusion contrast, coatability or printability, or solvent solubility is improved. If it is smaller than 350, the diffusion contrast is lowered, and if it is larger than 5000, the coatability or printability becomes poor.

  The impurity diffusion component (A) is, for example, NEW GLASS Vol. No. 22 2 2007 (p15-20), Journal of the Ceramic Society of Japan 111 [3] 2003 (p171-175), Journal of Non-crystalline Solids 306 (2002) 292-299, JP 2006-205725 A, etc. The production method may be referred to. For example, it can be obtained by reacting a bifunctional chlorosilane compound such as diphenyldichlorosilane or a trifunctional chlorosilane compound with phosphoric acid or the like in an inert gas atmosphere. The weight average molecular weight can be appropriately set by adjusting the temperature during the reaction.

Moreover, instead of the raw material chlorosilane compound, for example, a bifunctional or trifunctional silane compound represented by the following general formulas (3) to (4) may be used. Moreover, you may use the tetrafunctional alkoxysilane compound of following General formula (5) suitably. When these silane compounds are used, hydrogen chloride is not generated as a by-product, which is preferable.
R ³¹ Si (OR ³² ) _e (OR ³³ ) _f (OR ³⁴ ) _g (3)
R ⁴¹ R ⁴² Si (OR ⁴³ ) _h (OR ⁴⁴ ) _i (4)
Si (OR ²¹ ) _a (OR ²² ) _b (OR ²³ ) _c (OR ²⁴ ) _d (5)
[In General Formula (3), R ³¹ represents a hydrogen atom or an organic group. R ³² , R ³³ and R ³⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an aryl group. e, f, and g are integers that satisfy 0 ≦ e ≦ 3, 0 ≦ f ≦ 3, 0 ≦ g ≦ 3, and satisfy the condition of e + f + g = 3. ]
[In General Formula (4), ^R41 and ^R42 represent a hydrogen atom or an organic group. R ⁴³ and R ⁴⁴ each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an aryl group. h and i are integers satisfying 0 ≦ h ≦ 2, 0 ≦ i ≦ 2 and satisfying the condition of h + i = 2. ]
[In General Formula (5), R ²¹ , R ²² , R ²³ and R ²⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an aryl group. a, b, c and d are integers satisfying the condition of 0 ≦ a ≦ 4, 0 ≦ b ≦ 4, 0 ≦ c ≦ 4, 0 ≦ d ≦ 4 and a + b + c + d = 4. ]

  In the general formulas (3) to (4), the organic group is the same as the organic group for R, and is preferably an alkyl group, an aryl group or an alkenyl group which may have a substituent. In the general formulas (3) to (5), the alkyl group and the aryl group are the same as the alkyl group and aryl group having 1 to 5 carbon atoms exemplified in the above R. Specific examples of the bifunctional silane compound represented by the general formula (3) include methyldimethoxysilane, methylmethoxyethoxysilane, methyldiethoxysilane, methylmethoxypropoxysilane, methylmethoxypentyloxysilane, methylmethoxyphenyloxysilane, ethyl Dipropoxysilane, ethylmethoxypropoxysilane, ethyldipentyloxysilane, ethyldiphenyloxysilane, propyldimethoxysilane, propylmethoxyethoxysilane, propylethoxypropoxysilane, propyldiethoxysilane, propyldipentyloxysilane, propyldiphenyloxysilane, butyldimethoxy Silane, butylmethoxyethoxysilane, butyldiethoxysilane, butylethoxypropoxysilane, butyldipropoxy Silane, butylmethyldipentyloxysilane, butylmethyldiphenyloxysilane, dimethyldimethoxysilane, dimethylmethoxyethoxysilane, dimethyldiethoxysilane, dimethyldipentyloxysilane, dimethyldiphenyloxysilane, dimethylethoxypropoxysilane, dimethyldipropoxysilane, diethyldimethoxy Silane, diethylmethoxypropoxysilane, diethyldiethoxysilane, diethylethoxypropoxysilane, dipropyldimethoxysilane, dipropyldiethoxysilane, dipropyldipentyloxysilane, dipropyldiphenyloxysilane, dibutyldimethoxysilane, dibutyldiethoxysilane, dibutyl Dipropoxysilane, dibutylmethoxypentyloxysilane, dibutylmeth Siphenyloxysilane, methylethyldimethoxysilane, methylethyldiethoxysilane, methylethyldipropoxysilane, methylethyldipentyloxysilane, methylethyldiphenyloxysilane, methylpropyldimethoxysilane, methylpropyldiethoxysilane, methylbutyldimethoxysilane, Methylbutyldiethoxysilane, methylbutyldipropoxysilane, methylethylethoxypropoxysilane, ethylpropyldimethoxysilane, ethylpropylmethoxyethoxysilane, dipropyldimethoxysilane, dipropylmethoxyethoxysilane, propylbutyldimethoxysilane, propylbutyldiethoxysilane , Dibutylmethoxyethoxysilane, dibutylmethoxypropoxysilane, dibutylethoxypropoxy Examples include xysilane, phenyldimethoxysilane, phenylmethoxyethoxysilane, phenyldiethoxysilane, phenylmethoxypropoxysilane, phenylmethoxypentyloxysilane, and phenylmethoxyphenyloxysilane. Note that the alkyl group or alkoxy group having 3 or more carbon atoms in the above specific examples may be linear or branched. The butyl (or butoxy) group is preferably an n-butyl (n-butoxy) group. The same applies to the following specific examples.

  Specific examples of trifunctional silane compounds of the following general formula (4) include, for example, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, methyltripentyloxysilane, ethyltrimethoxysilane, Ethyltriethoxysilane, ethyltripropoxysilane, ethyltributoxysilane, ethyltripentyloxysilane, ethyltriphenyloxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltributoxysilane, propyltripentyloxysilane, propyltri Phenyloxysilane, butyltrimethoxysilane, butyltriethoxysilane, butyltripropoxysilane, butyltributoxysilane, butyltripentyloxysilane, butyl Riphenyloxysilane, methylmonomethoxydiethoxysilane, ethylmonomethoxydiethoxysilane, propylmonomethoxydiethoxysilane, butylmonomethoxydiethoxysilane, methylmonomethoxydipropoxysilane, methylmonomethoxydipentyloxysilane, methylmonomethoxy Diphenyloxysilane, ethylmonomethoxydipropoxysilane, ethylmonomethoxydipentyloxysilane, ethylmonomethoxydiphenyloxysilane, propylmonomethoxydipropoxysilane, propylmonomethoxydipentyloxysilane, propylmonomethoxydiphenyloxysilane, butylmonomethoxydi Propoxysilane, butylmonomethoxydipentyloxysilane, butylmonomethoxydiphenyloxysilane, Tylmethoxyethoxypropoxysilane, propylmethoxyethoxypropoxysilane, butylmethoxyethoxypropoxysilane, methylmonomethoxymonoethoxymonobutoxysilane, ethylmonomethoxymonoethoxymonobutoxysilane, propylmonomethoxymonoethoxymonobutoxysilane, butylmonomethoxymonoethoxy Examples include monobutoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane, and phenyltripentyloxysilane.

  Specific examples of the tetrafunctional silane compound represented by the following general formula (5) include, for example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetrapentyloxysilane, tetraphenyloxysilane, and trimethoxymonoethoxysilane. , Dimethoxydiethoxysilane, triethoxymonomethoxysilane, trimethoxymonopropoxysilane, monomethoxytributoxysilane, monomethoxytripentyloxysilane, monomethoxytriphenyloxysilane, dimethoxydipropoxysilane, tripropoxymonomethoxysilane, tri Methoxymonobutoxysilane, dimethoxydibutoxysilane, triethoxymonopropoxysilane, diethoxydipropoxysilane, tributoxymonopropoxysilane, di Toximonoethoxymonobutoxysilane, diethoxymonomethoxymonobutoxysilane, diethoxymonopropoxymonobutoxysilane, dipropoxymonomethoxymonoethoxysilane, dipropoxymonomethoxymonobutoxysilane, dipropoxymonoethoxymonobutoxysilane, dibutoxymono Examples thereof include tetraalkoxysilanes such as methoxymonoethoxysilane, dibutoxymonoethoxymonopropoxysilane, and monomethoxymonoethoxymonopropoxymonobutoxysilane. Among these, tetramethoxysilane and tetraethoxysilane are preferable from the viewpoint of reactivity.

  Moreover, the diffusing agent composition according to the embodiment may include an organic solvent. The organic solvent is not particularly limited. For example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, propylene glycol monomethyl Ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monopropyl ether, die Lenglycol monobutyl ether, diethylene glycol monophenyl ether, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, propylene glycol monomethyl ether Acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 2-methyl-3-methoxybutyl acetate, 2-ethoxybutyl acetate, 4- Toxibutyl acetate, 4-propoxybutyl acetate, methyl isobutyl ketone, ethyl isobutyl ketone, cyclohexanone, propyl propionate, isopropyl propionate, methyl-3-methoxypropionate, ethyl-3-methoxypropionate, ethyl-3- Ethoxypropionate, ethyl-3-propoxypropionate, propyl-3-methoxypropionate, isopropyl-3-methoxypropionate, butyl acetate, isoamyl acetate, methyl acetoacetate, methyl lactate, ethyl lactate, benzylmethyl Ether, benzyl ethyl ether, benzene, toluene, xylene, butanol, isobutanol, 3-methyl-3-methoxybutanol, hexanol, cyclohexanol, gamma butyrolactone, etc. Is mentioned. These may be used alone or in combination of two or more.

  According to the diffusing agent composition according to the embodiment described above, when heat treatment is performed as impurity diffusion treatment after substrate coating, -O-Si-O- bonds remaining after the heat treatment and phosphorus atoms as impurity diffusion components Can be prevented from being scattered by heat treatment. For this reason, the diffusion contrast of the part which apply | coats a diffusing agent composition, and the part which does not apply | coat a diffusing agent composition can be improved.

(Method for forming impurity diffusion layer and method for producing solar cell)
Referring to FIG. 1A to FIG. 1D and FIG. 2A to FIG. 2D, a diffusion composition film is formed or printed by applying the above diffusing agent composition to a semiconductor substrate. And a step of diffusing phosphorus atoms in the diffusing agent composition into the semiconductor substrate, and a method of forming an impurity diffusion layer, and a semiconductor substrate on which the impurity diffusion layer is formed A method for manufacturing a solar cell will be described. 1A to 1D and FIGS. 2A to 2D are cross-sectional views for explaining a method for manufacturing a solar cell including a method for forming an impurity diffusion layer according to an embodiment. FIG.

  First, as shown in FIG. 1A, a semiconductor substrate 1 such as a P-type silicon substrate is prepared. Then, as shown in FIG. 1B, a texture portion 1a having a fine concavo-convex structure is formed on one main surface of the semiconductor substrate 1 using a known wet etching method. Reflection of light on the surface of the semiconductor substrate 1 is prevented by the texture portion 1a. Subsequently, as shown in FIG. 1C, the diffusing agent composition 2 having the above-described aspect containing phosphorus atoms as an impurity diffusing component is applied to the main surface of the semiconductor substrate 1 on the textured portion 1a side.

  The diffusing agent composition 2 is applied to the surface of the semiconductor substrate 1 by a spin coating method, a roll coating printing method, a screen printing method, an ink jet printing method, or the like (in addition, when a pattern is formed instead of a coating film, a screen printing method is used). Etc. is preferable). After forming the impurity diffusing agent layer in this way, the diffusing agent composition 2 applied using a known means such as an oven is dried.

  Next, as shown in FIG. 1D, the semiconductor substrate 1 coated with the diffusing agent composition 2 is placed in an electric furnace and baked. After firing, phosphorus atoms in the diffusing agent composition 2 are diffused from the surface of the semiconductor substrate 1 into the semiconductor substrate 1 in an electric furnace. The diffusion temperature in the diffusion step is, for example, in the range of 800 to 1000 degrees. Instead of the electric furnace, the semiconductor substrate 1 may be heated by conventional laser irradiation. In this way, phosphorus atoms are diffused into the semiconductor substrate 1 to form the N-type impurity diffusion layer 3.

  Next, as shown in FIG. 2A, an unnecessary oxide film is removed by a known etching method. Then, as shown in FIG. 2B, a silicon nitride film (SiN film) is formed on the main surface of the semiconductor substrate 1 on the textured portion 1a side using a well-known chemical vapor deposition method (CVD method), for example, a plasma CVD method. A passivation film 4 made of a film is formed. This passivation film 4 also functions as an antireflection film.

  Next, as shown in FIG. 2C, the surface electrode 5 is patterned on the main surface of the semiconductor substrate 1 on the side of the passivation film 4 by, for example, screen printing of silver (Ag) paste. The surface electrode 5 is patterned to increase the efficiency of the solar cell. For example, the back electrode 6 is formed on the other main surface of the semiconductor substrate 1 by screen printing an aluminum (Al) paste.

  Next, as shown in FIG. 2D, the semiconductor substrate 1 on which the back electrode 6 is formed is placed in an electric furnace and baked, and then the aluminum on which the back electrode 6 is formed is transferred into the semiconductor substrate 1. To diffuse. Thereby, the electrical resistance on the back electrode 6 side can be reduced. Through the above steps, solar cell 10 according to the present embodiment can be manufactured.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art, and the embodiments to which such modifications are added are also possible. It is included in the scope of the present invention. A new embodiment generated by combining the above-described embodiment and the following modified example has the effects of the combined embodiment and modified example.

  The diffusing agent composition according to the above-described embodiment is employed in printing methods such as spin-on method, spray coating method, ink jet printing method, roll coat printing method, screen printing method, letterpress printing method, intaglio printing method, offset printing method and the like. You can also Of these, roll coat printing, screen printing, letterpress printing and intaglio printing are preferred.

  Examples of the present invention will be described below. However, these examples are merely examples for suitably explaining the present invention, and do not limit the present invention.

Example 1
Diphenyl as a raw material for an impurity diffusion component (A) (dopant component) having a —O—Si—O— bond and a —P (═O) n— bond [n is 1], which is a bond having a bifunctional group. Dichlorosilane (manufactured by Shin-Etsu Chemical) and phosphoric acid (manufactured by Junsei Chemical) were used. A rotary stirring blade was attached to the reaction vessel, phosphoric acid was added, and the inside of the system was replaced with an inert gas. While stirring at room temperature, diphenyldichlorosilane was dropped and reacted. In addition, the mixing ratio (molar ratio) of both was made into phosphoric acid: diphenyldichlorosilane = 2: 3 (ratio which Si-Cl and HO-P react in whole quantity).

  After completion of the reaction, the reaction vessel was heated to 200 ° C., and hydrogen chloride generated as a by-product was sufficiently degassed. Subsequently, the reaction vessel was naturally cooled to room temperature, and the reaction product was recovered. The obtained reaction product was crushed with a menor mortar, and a dopant component having a —O—Si—O— bond and a —P (═O) n— bond [n is 1], which is a bond having a bifunctional group, was obtained. Obtained. The weight average molecular weight was about 2000.

  1.0 g of this dopant component is dissolved in 9.0 g of propylene glycol monomethyl ether to prepare a diffusing agent composition, so that half the area is applied to a P-type (specific resistance: 5 to 15 Ω · cm) Si substrate. After spin coating, the solvent was removed by drying with a hot plate to form a single layer film containing a dopant component.

  Thermal diffusion (940 ° C., 30 minutes) was performed in an electric furnace on the Si substrate on which the single-layer film containing the dopant component was formed, and phosphorus atoms were diffused into the Si substrate to form an N layer. When the oxide film on the surface of the Si substrate was removed with dilute hydrofluoric acid and the sheet resistance was measured, the coated part was 14 Ω / □ and the uncoated part was> 18 KΩ / □, and the diffusion contrast was very large. It was.

(Example 2)
A dopant component was prepared in the same manner as in Example 1 except that diphenyldichlorosilane used in Example 1 was changed to diphenyldiethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.). In this example, the by-product is ethanol. Ethanol was removed from the dopant component by carrying out a vacuum treatment while heating to 50 ° C. The weight average molecular weight was about 500.

  After preparing 1.0 g of the obtained dopant component in 9.0 g of propylene glycol monomethyl ether to prepare a diffusing agent composition, the diffusing agent composition was applied to the Si substrate in the same manner as in Example 1 to form a single layer film. did. After forming the single layer film, thermal diffusion (940 ° C., 30 minutes) was performed in an electric furnace to diffuse phosphorus atoms into the Si substrate to form an N layer. When the oxide film on the surface of the Si substrate was removed with dilute hydrofluoric acid and the sheet resistance was measured, the coated part was 14 Ω / □ and the uncoated part was> 18 KΩ / □, and the diffusion contrast was very large. It was.

(Example 3)
A dopant component was prepared in the same manner as in Example 1 except that diphenyldichlorosilane used in Example 1 was changed to diphenyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.). In this example, the by-product is methanol. Ethanol was removed from the dopant component by carrying out a vacuum treatment while heating to 50 ° C. The weight average molecular weight was about 500.

  After preparing 1.0 g of the obtained dopant component in 9.0 g of propylene glycol monomethyl ether to prepare a diffusing agent composition, the diffusing agent composition was applied to the Si substrate in the same manner as in Example 1 to form a single layer film. did. After forming the single layer film, thermal diffusion (940 ° C., 30 minutes) was performed in an electric furnace to diffuse phosphorus atoms into the Si substrate to form an N layer. When the oxide film on the surface of the Si substrate was removed with dilute hydrofluoric acid and the sheet resistance was measured, the coated part was 14 Ω / □ and the uncoated part was> 18 KΩ / □, and the diffusion contrast was very large. It was.

Example 4
A dopant component was prepared in the same manner as in Example 1 except that diphenyldichlorosilane used in Example 1 was changed to dimethyldichlorosilane (manufactured by Shin-Etsu Chemical Co., Ltd.). In this example, the by-product is hydrogen chloride. While heating to 200 ° C., hydrogen chloride generated as a by-product was sufficiently degassed. The weight average molecular weight was about 400.

  After preparing 1.0 g of the obtained dopant component in 9.0 g of propylene glycol monomethyl ether to prepare a diffusing agent composition, the diffusing agent composition was applied to the Si substrate in the same manner as in Example 1 to form a single layer film. did. After forming the single layer film, thermal diffusion (940 ° C., 30 minutes) was performed in an electric furnace to diffuse phosphorus atoms into the Si substrate to form an N layer. When the oxide film on the surface of the Si substrate was removed with dilute hydrofluoric acid and the sheet resistance value was measured, the applied part was 17Ω / □, the uncoated part was 3,500Ω / □, and the diffusion contrast was very large. there were.

(Comparative Example 1)
As a dopant component having an Si—O—P skeleton, tristrimethylsilyl phosphate (manufactured by Tokyo Chemical Industry, molecular weight 314.54) was used. This and PPSQ-E (manufactured by Konishi Chemical Industries) were dissolved in propylene glycol monomethyl ether, and the diffusing agent composition was adjusted so as to match the silicon / phosphorus ratio in the sample of Example 1. This solution is spin-coated so that a half area is applied to a P-type (specific resistance: 5 to 15 Ω · cm) Si substrate, then the solvent is removed by drying with a hot plate, and a single-layer film containing a dopant component Formed.

Thermal diffusion (940 ° C., 30 minutes) was performed in an electric furnace on the Si substrate on which the single-layer film containing the dopant component was formed, and phosphorus atoms were diffused into the Si substrate to form an N layer. When the oxide film on the surface of the Si substrate was removed with dilute hydrofluoric acid and the sheet resistance value was measured, the coated part was 25 Ω / □ and the uncoated part was 900 Ω / □, which was a diffusion contrast compared to Examples 1-4. Became small.
(Comparative Example 2)
A dopant component was prepared in the same manner as in Example 1 except that the diphenyldichlorosilane used in Example 1 was changed to tetraethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.), but it was gelled and a dopant component could not be obtained. It was.

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate, 1a Texture part, 2 Diffusing agent composition, 3 N-type impurity diffusion layer, 4 Passivation film, 5 Surface electrode, 6 Back electrode, 10 Solar cell

Claims (3)

A diffusing agent composition containing an impurity diffusing component and used for forming an impurity diffusing layer on a semiconductor substrate,
The impurity diffusion component has a weight average molecular weight of 350 to 5000, and has an —O—Si—O— bond and a —P (═O) n— bond [n is 0 or 1],
A diffusing agent composition in which the -O-Si-O- bond is a bond having a 2-3 functional group represented by the following formula.

[Wherein, each R is independently an organic group or a hydroxyl group. ] The diffusing agent composition according to claim 1, wherein the impurity diffusion component has a skeleton represented by the following formula.

[Wherein, X is independently R or bridging oxygen (wherein at least one X is R), Y is independently R or bridging oxygen, and n is 0 or 1] . ] A pattern forming step of forming a pattern by applying the diffusing agent composition according to claim 1 or 2 to a semiconductor substrate;
A diffusion step of diffusing phosphorus atoms in the diffusing agent composition into the semiconductor substrate;
A method for forming an impurity diffusion layer, comprising:

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