JPWO2019176716A1 - Impurity diffusion composition, manufacturing method of semiconductor device using it, and manufacturing method of solar cell - Google Patents

Abstract

An object of the present invention is to provide an impurity diffusion composition which is excellent in storage stability of a coating liquid and enables continuous printability at the time of screen printing and uniform diffusion on a semiconductor substrate. In order to achieve the above object, the impurity diffusion composition of the present invention is (A) a polymer having at least one structure selected from the following general formulas (1) and (2) in the side chain (hereinafter, (A) polymer). ), And (B) contains an impurity diffusion component. (In the general formulas (1) and (2), R1 to R14 each independently represent a hydrogen atom or an organic group having 1 to 8 carbon atoms. A1 represents an integer of 1 to 4. a2 and a3 each independently indicate an integer of 0 to 2. a2 + a3 indicates an integer of 0 to 3. * Indicates a bonding portion with a polymer.)

Description

The present invention relates to an impurity diffusion composition for diffusing impurities in a semiconductor substrate, a method for manufacturing a semiconductor element using the same, and a method for manufacturing a solar cell.

Currently, in the manufacture of solar cells, when a p-type or n-type impurity diffusion layer is formed in a semiconductor substrate, a method of forming a diffusion source on the substrate and diffusing impurities in the semiconductor substrate by thermal diffusion is used. It has been taken. A CVD method and a solution coating method of a liquid impurity diffusion composition have been studied for forming a diffusion source. Among them, the solution coating method is suitable because it does not require expensive equipment and is excellent in mass productivity. Used for. When a p-type impurity diffusion layer is formed by a solution coating method, a coating liquid containing a boron compound and a hydroxyl group-containing polymer compound such as polyvinyl alcohol is usually applied to the surface of a semiconductor substrate by a spin coating method or a screen printing method. (See, for example, Patent Document 1).

However, in the boron-containing diffusion composition described in Patent Document 1, since the boron compound is stabilized by the hydroxyl group of the hydroxyl group-containing polymer compound, a binder containing a large amount of hydroxyl groups is required to contain the boron compound at a high concentration. It was necessary to use resin. Since such a hydroxyl group-containing polymer compound has poor solubility in an organic solvent, it is necessary to contain a large amount of water in the composition. However, water tends to contain metal impurities, which deteriorates the performance of the solar cell. I will let you. Further, when a large amount of water is contained, there are problems that the solubility of other organic compounds in the composition is lowered, the storage stability of the solution is lowered, and continuous printing at the time of screen printing is difficult. Therefore, a coating liquid to which a polyhydric alcohol is added has been proposed as an alternative to a hydroxyl group-containing polymer compound such as polyvinyl alcohol (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 9-181010 Japanese Unexamined Patent Publication No. 2013-77804

However, the coating liquid to which the polyhydric alcohol is added as described in Patent Document 2 has a problem that the diffusion uniformity of impurities is inferior.

The present invention has been made based on the above circumstances, has excellent storage stability of the coating liquid, and enables continuous printability at the time of screen printing and uniform diffusion on a semiconductor substrate. An object of the present invention is to provide an impurity diffusion composition.

In order to solve the above problems, the impurity diffusion composition of the present invention has the following constitution. That is, the impurity diffusion composition of the present invention comprises (A) a polymer having at least one structure selected from the following general formulas (1) and (2) in the side chain (hereinafter referred to as (A) polymer), and (B) Contains an impurity diffusion component.

In the general formulas (1) and (2), R ^{1 to} R ¹⁴ each independently represent a hydrogen atom or an organic group having 1 to 8 carbon atoms. a ₁ represents an integer of ₁ to 4, and a ₂ and a ₃ independently represent an integer of 0 to 2. a ₂ + a ₃ indicates an integer from 0 to 3. * Indicates the bond with the polymer.

According to the present invention, it is possible to provide an impurity diffusion composition which is excellent in storage stability, can improve continuous printability at the time of screen printing, and can be uniformly diffused onto a semiconductor substrate.

It is a process sectional view which shows the manufacturing method of the semiconductor element which concerns on 1st Embodiment of this invention. It is a process sectional view which shows the manufacturing method of the semiconductor element which concerns on 2nd Embodiment of this invention. It is a process sectional view which shows the manufacturing method of the back surface bonding type solar cell using the manufacturing method of the semiconductor element which concerns on 2nd Embodiment of this invention. It is a process sectional view which shows the manufacturing method of the semiconductor element which concerns on 3rd Embodiment of this invention. It is a process sectional view which shows the manufacturing method of the double-sided power generation type solar cell using the manufacturing method of the semiconductor element which concerns on 3rd Embodiment of this invention. It is a process sectional view which shows the manufacturing method of the semiconductor element which concerns on 4th Embodiment of this invention. It is a process sectional view which shows an example of the barrier property evaluation using the impurity diffusion composition of this invention.

Hereinafter, a preferred embodiment of the impurity diffusion composition according to the present invention and a method for producing a semiconductor device using the same will be described in detail with reference to the drawings as necessary. The present invention is not limited to these embodiments.

The impurity diffusion composition of the present invention may be referred to as (A) a polymer containing at least one structure selected from the general formulas (1) and (2) in the side chain (hereinafter, simply referred to as "(A) polymer"). ), And (B) contains an impurity diffusion component.

In the general formulas (1) and (2), R ^{1 to} R ¹⁴ each independently represent a hydrogen atom or an organic group having 1 to 8 carbon atoms. a ₁ represents an integer of ₁ to 4, and a ₂ and a ₃ independently represent an integer of 0 to 2. a ₂ + a ₃ indicates an integer from 0 to 3. * Indicates the bond with the polymer.

(A) Polymer In the impurity diffusion composition of the present invention, the polymer (A) reacts with the impurity diffusion component (B) to form a complex, for example, to form a uniform coating film when the composition is applied. It is an ingredient that makes it possible. This enables uniform diffusion of impurities on the semiconductor substrate.

Further, since the reaction product of the polymer (A) and the impurity diffusion component (B) is soluble in an organic solvent, the impurity diffuser composition of the present invention does not have to contain a large amount of water. Therefore, it is possible to improve the storage stability of the coating liquid, improve the continuous printability at the time of screen printing, and uniformly diffuse the coating liquid on the semiconductor substrate while suppressing the deterioration of the performance of the solar cell.

The polymer in the present invention may contain an oligomer, and specifically refers to a polymer having a degree of polymerization of 2 or more. The degree of polymerization is preferably 2 to 100, more preferably 5 to 50.

The content of the polymer (A) in the impurity diffusion composition of the present invention is determined by the coating method and the required resistance value, but is preferably 0.01 to 50% by mass with respect to the total amount of the impurity diffusion composition. 1 to 20% by mass is more preferable.

Examples of the organic group having 1 to 8 carbon atoms in R ^{1 to} R ¹⁴ include an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms. The alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms may be an unsubstituted or substituted product, and can be selected according to the characteristics of the composition.

Specific examples of alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, n-hexyl group, trifluoromethyl group, 3, Examples thereof include 3,3-trifluoropropyl group, 3-methoxy-n-propyl group, glycidyl group, 3-glycidoxypropyl group, 3-aminopropyl group, 3-mercaptopropyl group and 3-isocyanuppropyl group. However, from the viewpoint of suppressing the peeling residue of the diffusion composition after the diffusion of impurities, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group and t-butyl group having 4 or less carbon elements are preferable.

Specific examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a t-butoxy group and the like.

The polymer (A) is preferably a polymer made of siloxane or acrylic from the viewpoint of (B) formability of a complex with an impurity diffusion component and stability of the formed complex.

(Polymer consisting of siloxane)
From the viewpoint of masking property against different kinds of impurities and suppression of outdiffusion of impurities, the polymer (A) is preferably a polymer composed of siloxane, and has a partial structure represented by any of the general formulas (3) and (4). , A polymer composed of a siloxane containing at least one of the partial structures represented by any of the general formulas (5) and (6) is more preferable.

R ¹⁵ represents an alkylene group having 1 to 8 carbon atoms. R ¹⁶ represents any one of a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and an acyl group having 2 to 6 carbon atoms. R ¹⁷ and R ¹⁸ have a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an acyl group having 2 to 6 carbon atoms, and 6 to 15 carbon atoms. Represents any of the aryl groups. X represents at least one structure selected from the general formulas (1) and (2). Further, the proportion of the partial structure represented by any of the general formulas (3) and (4) in the siloxane structure is less than 5 to 100 mol%.

At least one structure selected from the general formulas (1) and (2) by making the proportion of the partial structure represented by any of the general formulas (3) and (4) in the siloxane structure 5% or more. And (B) the impurity diffusing component sufficiently form a complex, and the diffusibility of the impurity is further improved.

Further, R ¹⁷ is an aryl group having 6 to 15 carbon atoms, and the proportion of the partial structure represented by any of the general formulas (5) and (6) in the siloxane structure is 5 to 95 mol%. However, it is more preferable from the viewpoint of masking property against different kinds of impurities and suppression of outdiffusion of impurities, and further preferably 10 to 90 mol% from the viewpoint of peelability of the diffusing agent and the mask after thermal diffusion.

By setting the proportion of the partial structure represented by any of the general formulas (5) and (6) in the siloxane structure to 5 mol% or more, the crosslink density between the siloxane skeletons does not become too high, and even a thick film cracks. Is more suppressed. As a result, cracks are less likely to occur in the firing and heat diffusion steps, so that the stability of impurity diffusion can be improved. Further, after the heat diffusion of impurities, the impurity diffusion layer can be used as a mask for other impurity diffusers. In order to have masking properties, it is better that the film thickness after diffusion is large, and the impurity diffusion composition of the present invention, which is less likely to crack even in a thick film, can be preferably used. Further, even in a composition to which a thermal decomposition component such as a thickener is added, the reflow effect of siloxane makes it possible to fill the pores generated by the thermal decomposition, and it is possible to form a dense film with few pores. it can. Therefore, it is not easily affected by the atmosphere at the time of diffusion, and a high masking property against other impurities can be obtained.

On the other hand, by setting the proportion of the partial structure represented by any of the general formulas (5) and (6) in the siloxane structure to 95 mol% or less, it is possible to eliminate the peeling residue of the diffusion composition after impurity diffusion. It will be possible. The residue is considered to be a carbide that remains without completely decomposing and volatilizing the organic matter, which not only inhibits the doping property but also increases the contact resistance with the electrode formed later, which causes the efficiency of the solar cell to decrease. It becomes.

The proportion of the partial structure represented by any of the general formulas (3) and (4) in the siloxane structure is determined by, for example, measuring the ²⁹ Si-NMR spectrum of polysiloxane, and the peak area of Si to which X is bonded and X. It can be obtained from the ratio of the peak areas of Si to which is not bonded.

The proportion of the partial structure represented by any of the general formulas (5) and (6) in the siloxane structure is, for example, the peak area of Si to which the aryl group is bonded by measuring the ²⁹ Si-NMR spectrum of polysiloxane. It can be obtained from the ratio of the peak areas of Si to which the aryl group is not bonded.

Examples of the alkylene group having 1 to 8 carbon atoms in R ¹⁵ include a methylene group, an ethylene group, a propylene group, a butylene group, a hexylene group, a heptylene group, an octylene group and the like.

The aryl group having 6 to 15 carbon atoms in R ¹⁷ and R ¹⁸ may be an unsubstituted or substituted product, and can be selected according to the characteristics of the composition. Specific examples of aryl groups having 6 to 15 carbon atoms include phenyl group, p-tolyl group, m-tolyl group, o-tolyl group, p-hydroxyphenyl group, p-styryl group, p-methoxyphenyl group and naphthyl. Examples thereof include a phenyl group, a p-tolyl group, and an m-tolyl group.

Alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, alkenyl groups having 2 to 10 carbon atoms, and acyloxy groups having 2 to 6 carbon atoms in R ¹⁶ , R ¹⁷ , and R ¹⁸ are all unsubstituted. , Substituents may be used, and can be selected according to the characteristics of the composition.

Specific examples of the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms include the same as those in R ^{1 to} R ¹⁴ .

Specific examples of the alkenyl group having 2 to 10 carbon atoms include a vinyl group, a 1-propenyl group, a 1-butenyl group, a 2-methyl-1-propenyl group, a 1,3-butandienyl group, and a 3-methoxy-1-propenyl. Groups, 3-acryloxypropyl group, 3-methacryloxypropyl group and the like can be mentioned, but from the viewpoint of suppressing the peeling residue of the diffusion composition after impurity diffusion, a vinyl group having 4 or less carbon atoms, a 1-propenyl group, etc. A 1-butenyl group, a 2-methyl-1-propenyl group, a 1,3-butandienyl group and a 3-methoxy-1-propenyl group are particularly preferable.

Specific examples of the acyloxy group having 2 to 6 carbon atoms include an acetoxy group, a propionyloxy group, an acryloyloxy group and the like.

As a specific example of organosilane which is a raw material of a unit having R ¹⁵ , R ¹⁶ and X having a partial structure represented by any of the general formulas (3) and (4), TMSOX (trimethoxysilyloxetane, Toagosei) Co., Ltd.), TESOX (triethoxysilyloxetane, Toagosei Co., Ltd.) are preferable.

Specific examples of the organosilane as a raw material of the unit having the partial structures R ¹⁷ and R ^{18 represented} by the general formulas (5) and (6) include phenyltrimethoxysilane, phenyltriethoxysilane, and p-. Hydroxyphenyltrimethoxysilane, p-tolyltrimethoxysilane, p-styryltrimethoxysilane, p-methoxyphenyltrimethoxysilane, diphenyldimethoxysilane, methylphenyldimethoxysilane, 1-naphthyltrimethoxysilane, 2-naphthyltrimethoxysilane , 1-naphthylriethoxysilane and 2-naphthylriethoxysilane are preferable, and phenyltrimethoxysilane, p-tolyltrimethoxysilane, and p-methoxyphenyltrimethoxysilane are particularly preferable.

A polymer composed of a siloxane containing at least one of a partial structure represented by any of the general formulas (3) and (4) and a partial structure represented by any of the general formulas (5) and (6) is a polymer. It can be obtained by hydrolyzing an organosilane compound and then subjecting the hydrolyzate to a condensation reaction in the presence of a solvent or in the absence of a solvent.

Further, during the above reaction, the structure of the general formula (1) or (2) can be expressed by opening the ring of the oxetane structure in the organosilane as a raw material. As a result, the structure of the general formula (1) or (2) and the impurity diffusion component (B) sufficiently form a complex, and good diffusibility can be obtained. The ring-opening rate of oxetane is preferably 5% or more.

Various conditions of the hydrolysis reaction, for example, the content of the acid catalyst, the reaction temperature, the reaction time, etc. can be appropriately set in consideration of the reaction scale, the size, the shape of the reaction vessel, etc., but for example, in a solvent, It is preferable to add an acid catalyst and water to the organosilane compound over 1 to 180 minutes and then react at 20 ° C. to 110 ° C. for 1 to 180 minutes. By carrying out the hydrolysis reaction under such conditions, a rapid reaction can be suppressed. The reaction temperature is more preferably 30 to 130 ° C.

The hydrolysis reaction is preferably carried out in the presence of an acid catalyst. Acid catalysts include hydrogen halide-based inorganic acids such as hydrochloric acid, hydrobromic acid, and hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, hexafluorophosphate, hexafluoroantimonic acid, boric acid, and tetrafluoroboric acid. Other inorganic acids such as chromic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, sulfonic acid such as trifluoromethanesulfonic acid, acetic acid, citric acid, formic acid, gluconic acid, lactic acid, oxalic acid, Carous acids such as tartrate acid, pyruvate, citric acid, succinic acid, fumaric acid and malic acid can be exemplified. In the present invention, the acid catalyst preferably contains atoms other than silicon, hydrogen, carbon, oxygen, nitrogen, and phosphorus as much as possible from the viewpoint of doping property, and acid catalysts of phosphoric acid, formic acid, acetic acid, and various carboxylic acids are used. Is preferable. Of these, phosphoric acid is preferable.

The preferable content of the acid catalyst is preferably 0.1 part by weight to 5 parts by weight with respect to 100 parts by weight of the total organosilane compound used in the hydrolysis reaction. By setting the amount of the acid catalyst in the above range, the hydrolysis reaction can be easily controlled so as to proceed sufficiently and sufficiently.

The solvent used for the hydrolysis reaction of the organosilane compound and the condensation reaction of the hydrolyzate is not particularly limited, and can be appropriately selected in consideration of the stability, coatability, volatility and the like of the resin composition. Further, two or more kinds of solvents may be combined, or the reaction may be carried out without a solvent.

In the present invention, from the viewpoint of solubility and printability, diethylene glycol methyl ethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, methyl lactate, ethyl lactate, diacetone alcohol, propylene glycol monomethyl ether acetate, 3-methoxy. -3-Methyl-1-butanol, dipropylene glycol monomethyl ether, dipropylene glycol-n-butyl ether, γ-butyrolactone, diethylene glycol monoethyl ether acetate, butyl diglycol acetate, ethyl acetoacetate, N-methyl-2-pyrrolidone, Preferable examples include N, N-dimethylimidazolidinone, dipropylene glycol methyl ether acetate, 1,3-butylene glycol diacetate, diisobutyl ketone, propylene glycol t-butyl ether, and propylene glycol n-butyl ether.

When a solvent is produced by the hydrolysis reaction, it can be hydrolyzed without a solvent. After completion of the reaction, it is also preferable to adjust the concentration to an appropriate level as the resin composition by further adding a solvent. Further, depending on the purpose, after hydrolysis, an appropriate amount of the produced alcohol or the like may be distilled off and removed under heating and / or reduced pressure, and then a suitable solvent may be added.

The amount of the solvent used in the hydrolysis reaction is preferably 80 parts by weight or more and 500 parts by weight or less with respect to 100 parts by weight of the total organosilane compound. By setting the amount of the solvent in the above range, the hydrolysis reaction can be easily controlled so as to proceed sufficiently and sufficiently. The water used for the hydrolysis reaction is preferably ion-exchanged water. The amount of water can be arbitrarily selected, but it is preferably used in the range of 1.0 to 4.0 mol per 1 mol of Si atom.

(Polymer made of acrylic)
As the polymer (A), a polymer made of acrylic containing a partial structure represented by the general formula (7) and a partial structure represented by the general formula (8) is also preferable.

R ¹⁹ and R ²¹ each independently represent either a hydrogen atom, a halogen, an alkyl group having 1 to 4 carbon atoms or a fluoroalkyl group having 1 to 4 carbon atoms. R ²⁰ represents an alkylene group having 1 to 8 carbon atoms. R ²² represents an alkyl group having 1 to 4 carbon atoms. X represents at least one structure selected from the general formulas (1) and (2). a ₄ and a ₅ represent an integer of 0 or 1, and at least one of a ₄ and a ₅ is 1. Further, the proportion of the partial structure represented by the general formula (7) in the acrylic structure is less than 5 to 100 mol%.

By setting the proportion of the partial structure represented by the general formula (7) in the acrylic structure to 5 mol% or more, at least one structure selected from the general formulas (1) and (2) and (B) impurity diffusion. The components sufficiently form a complex, and the diffusibility of the (B) impurity diffusing component is further improved.

Examples of the alkyl group having 1 to 4 carbon atoms in R ¹⁹ and R ²¹ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group and the like. Examples of the fluoroalkyl group having 1 to 4 carbon atoms include a trifluoromethyl group and a 3,3,3-trifluoropropyl group. Examples of the alkylene group having 1 to 8 carbon atoms in R ²⁰ include a methylene methylene group, an ethylene group, a propylene group, a butylene group, a hexylene group, a heptylene group, an octylene group and the like. Examples of the alkyl group having 1 to 4 carbon atoms in R ²² include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group and the like.

Specific examples of the acrylic monomer used as a raw material for the unit having the partial structures R ¹⁹ , R ²⁰ and X represented by the general formula (7) are (3-ethyloxetane-3-yl) methyl acrylate (Osaka Organic Chemical Industry Co., Ltd.). Co., Ltd.). Specific examples of the acrylic monomer used as a raw material for the unit having R ²¹ and R ²² having a partial structure represented by the general formula (8) include acrylic acid. Examples of the radical polymerization initiator include azobisisobutyronitrile. The solvent is not particularly limited and can be appropriately selected in consideration of the stability, coatability, volatility and the like of the resin composition. Further, two or more kinds of solvents may be combined, or the reaction may be carried out without a solvent. Specific examples of the solvent include those similar to the siloxane polymerization.

(B) Impurity Diffusion Component In the impurity diffusion composition of the present invention, the (B) impurity diffusion component is a component for forming an impurity diffusion layer in a semiconductor substrate.

The p-type impurity diffusion component is preferably a compound containing elements of the 13 genera, and more preferably a boron compound.

Examples of the boron compound include boric acid, diboron trioxide, methylboronic acid, phenylboronic acid, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, trioctyl borate, and triphenyl borate. it can.

The n-type impurity diffusion component is preferably a compound containing a Group 15 element, and more preferably a phosphorus compound.

Phosphoric compounds include diphosphoric pentoxide, phosphoric acid, polyphosphoric acid, methyl phosphate, dimethyl phosphate, trimethyl phosphate, ethyl phosphate, diethyl phosphate, triethyl phosphate, propyl phosphate, dipropyl phosphate, and phosphoric acid. Phosphate esters such as tripropyl, butyl phosphate, dibutyl phosphate, tributyl phosphate, phenyl phosphate, diphenyl phosphate, triphenyl phosphate, methyl phosphite, dimethyl phosphite, trimethyl borophosphate, sub Ethyl phosphate, diethyl phosphite, triethyl phosphite, propyl phosphite, dipropyl phosphite, tripropyl phosphite, butyl phosphite, dibutyl phosphite, tributyl phosphite, phenyl phosphite, Examples thereof include phosphite esters such as diphenyl phosphite and triphenyl phosphite. Of these, phosphoric acid, diphosphorus pentoxide or polyphosphoric acid is preferable from the viewpoint of doping property.

The amount of the (B) impurity diffusion component contained in the impurity diffusion composition can be arbitrarily determined by the resistance value required for the semiconductor substrate, but is 0.1 to 10% by mass with respect to the total amount of the impurity diffusion composition. Is preferable.

(C) Solvent The impurity diffusion composition of the present invention preferably contains a solvent. The solvent can be used without particular limitation, but a solvent having a boiling point of 100 ° C. or higher is preferable from the viewpoint of further improving printability when a screen printing method, a spin coating printing method, or the like is used. When the boiling point is 100 ° C. or higher, for example, when the impurity diffusion composition is printed on the printing plate used in the screen printing method, it is possible to prevent the impurity diffusion composition from drying and sticking on the printing plate. The content of the solvent having a boiling point of 100 ° C. or higher is preferably 20% by weight or more based on the total amount of the solvent.

(D) Surfactant The impurity diffusion composition of the present invention may contain a surfactant. By containing a surfactant, uneven coating is improved and a more uniform coating film can be obtained. As the surfactant, a fluorine-based surfactant or a silicone-based surfactant is preferably used. When added, the content of the surfactant is preferably 0.0001 to 1% by weight in the impurity diffusion composition.

(E) Thickener The impurity diffusion composition of the present invention preferably contains a thickener for adjusting the viscosity. As a result, it is possible to apply a more precise pattern by a printing method such as screen printing.
The thickener preferably has a 90% thermal decomposition temperature of 400 ° C. or lower from the viewpoint of forming a dense film and reducing residues. Specifically, polyethylene glycol, polyethylene oxide, polypropylene glycol, polypropylene oxide, and acrylic acid ester-based resins are preferable, and polyethylene oxide, polypropylene oxide, and acrylic acid ester-based resins are particularly preferable. From the viewpoint of storage stability, acrylic ester-based resins are particularly preferable. Here, the 90% thermal decomposition temperature is a temperature at which the weight of the thickener is reduced by 90% due to thermal decomposition. The thermal decomposition temperature can be measured using a thermogravimetric analyzer (TGA) or the like.

The content of these thickeners is preferably 3% by weight or more and 20% by weight or less in the impurity diffusion composition. Within this range, a sufficient viscosity adjusting effect can be easily obtained, and at the same time, a more dense film can be formed.

(F) Impurity Diffusion Composition The impurity diffusion composition of the present invention preferably contains a tix agent that imparts tix property from the viewpoint of screen printability. Here, imparting the thixo property means increasing the ratio (η ₁ / η ₂ ) of the viscosity (η ₁ ) at the time of low shear stress and the viscosity (η ₂ ) at the time of high shear stress. The pattern accuracy of screen printing can be further improved by containing the thixogen. The reason is as follows. Since the impurity diffusion composition containing a thixogen has a low viscosity at high shear stress, clogging of the screen is unlikely to occur during screen printing, and the viscosity is high at low shear stress, so that bleeding immediately after printing and thickening of the pattern line width occur. Is less likely to occur.

Further, it is more preferable to use it in combination with the above-mentioned thickener, and a higher effect can be obtained.

The viscosity of the impurity diffusion composition of the present invention is not limited and can be appropriately changed depending on the printing method and the film thickness. Here, for example, in the case of the screen printing method, which is one of the preferable printing forms, the viscosity of the diffusion composition is preferably 5,000 mPa · s or more. This is because bleeding of the print pattern can be suppressed and a good pattern can be obtained. A more preferable viscosity is 10,000 mPa · s or more. There is no particular upper limit, but 100,000 mPa · s or less is preferable from the viewpoint of storage stability and handleability.

Here, when the viscosity is less than 1,000 mPa · s, it is a value measured at a rotation speed of 20 rpm using an E-type digital viscometer based on JIS Z 8803 (1991) “Solution Viscosity-Measurement Method”. In the case of 1,000 mPa · s or more, it is a value measured at a rotation speed of 20 rpm using a B-type digital viscometer based on JIS Z 8803 (1991) “Solution Viscosity-Measuring Method”.

The tixo property can be determined from the ratio of viscosities at different rotation speeds obtained by the above viscosity measuring method. In the present invention, the ratio (η ₂ / η ₂₀ ) of the viscosity (η ₂₀ ) at a rotation speed of 20 rpm to the viscosity (η ₂ ) at a rotation speed of 2 rpm is defined as the thixo property. In order to form a pattern with high accuracy in screen printing, it is preferable that the ticking property is 2 or more, and 3 or more is more preferable.

The impurity diffusion composition of the present invention is not particularly limited in solid content concentration, but is preferably in the range of 1% by weight or more and 90% by weight or less. If it is lower than this concentration range, the coating film thickness becomes too thin and it is difficult to obtain the desired doping property and masking property, and if it is higher than this concentration range, the storage stability may decrease.

<Manufacturing method of semiconductor elements>
The first embodiment of the method for manufacturing a semiconductor device of the present invention includes a step of applying the impurity diffusion composition of the present invention to a semiconductor substrate to form an impurity diffusion composition film, and a step of removing impurities from the impurity diffusion composition film. It includes a step of diffusing to form an impurity diffusion layer on a semiconductor substrate.

A second embodiment of the method for manufacturing a semiconductor device of the present invention includes a step of applying an n-type impurity diffusion composition to a semiconductor substrate to form an n-type impurity diffusion composition film, and a p-type after the step. A step of applying the impurity diffusion composition of the present invention, which is an impurity diffusion composition and (B) the impurity diffusion component is a boron compound, to the semiconductor substrate to form a p-type impurity diffusion composition film, and the semiconductor substrate. It includes a step of simultaneously forming an n-type impurity diffusion layer and a p-type impurity diffusion layer on the semiconductor substrate by heating.

Further, the third embodiment of the method for manufacturing a semiconductor device of the present invention is a p-type impurity diffusion composition on one surface of a semiconductor substrate, and (B) the impurity diffusion of the present invention in which the impurity diffusion component is a boron compound. A step of applying the composition to form a p-type impurity diffusion composition film, and a step of applying an n-type impurity diffusion composition to the other surface of the semiconductor substrate to form an n-type impurity diffusion composition film. This is a method for manufacturing a semiconductor device, which comprises a step of simultaneously forming a p-type impurity diffusion layer and an n-type impurity diffusion layer on the semiconductor substrate by heating the semiconductor substrate.

Further, the fourth embodiment of the method for manufacturing a semiconductor element of the present invention is a method for manufacturing a semiconductor device using a plurality of semiconductor substrates, and includes the following steps (a) to (c), (b). In the steps (c) and (c), a pair of semiconductor substrates are arranged so that the surfaces on which the first conductive type impurity diffusion composition films are formed face each other.
(A) A step of applying the impurity diffusion composition of the present invention to one surface of each semiconductor substrate to form a first conductive type impurity diffusion composition film.
(B) The semiconductor substrate on which the first conductive type impurity diffusion composition film is formed is heated to diffuse the first conductive type impurities into the semiconductor substrate to form a first conductive type impurity diffusion layer. The process of forming.
(C) The semiconductor substrate is heated in an atmosphere having a gas containing the second conductive type impurities to diffuse the second conductive type impurities on the other surface of the semiconductor substrate to diffuse the second conductive type impurities. The process of forming a diffusion layer.

Hereinafter, a method for forming an impurity diffusion layer applicable to the method for manufacturing these semiconductor elements will be described with reference to the drawings. All of these are examples, and the methods applicable to the method for manufacturing a semiconductor device of the present invention are not limited to these.

(First Embodiment)
FIG. 1 shows an example of a first embodiment of the method for manufacturing a semiconductor device of the present invention. First, as shown in FIG. 1A, the p-type impurity diffusion composition film 12 is formed on the semiconductor substrate 11.

Examples of the semiconductor substrate include n-type single crystal silicon having an impurity concentration of 10 ¹⁵ to ¹⁶ atoms / cm ³ , polycrystalline silicon, and crystalline silicon substrate in which other elements such as germanium and carbon are mixed. Can be mentioned. It is also possible to use p-type crystalline silicon or a semiconductor other than silicon. The semiconductor substrate is preferably a substantially quadrangle having a thickness of 50 to 300 μm and an outer shape of 100 to 250 mm on a side. Further, in order to remove slice damage and a natural oxide film, it is preferable to etch the surface with a hydrofluoric acid solution or an alkaline solution.

A protective film may be formed on the light receiving surface of the semiconductor substrate. As this protective film, a known protective film such as silicon oxide or silicon nitride, which is formed by a method such as a CVD (chemical vapor deposition) method or a spin-on-glass (SOG) method, can be applied.

Examples of the method for applying the impurity diffusion composition include a spin coating method, a screen printing method, an inkjet printing method, a slit coating method, a spray coating method, a letterpress printing method, and an intaglio printing method.

After forming the coating film by these methods, it is preferable to dry the impurity diffusion composition film on a hot plate, an oven or the like in the range of 50 to 200 ° C. for 30 seconds to 30 minutes. The film thickness of the impurity diffusion composition film after drying is preferably 100 nm or more from the viewpoint of the diffusibility of impurities, and preferably 3 μm or less from the viewpoint of the residue after etching.

Next, as shown in FIG. 1B, impurities are diffused on the semiconductor substrate 11 to form the p-type impurity diffusion layer 13.

As a method for diffusing impurities, a known heat diffusing method can be used, and for example, a method such as electric heating, infrared heating, laser heating, or microwave heating can be used.

The time and temperature of thermal diffusion can be appropriately set so as to obtain desired diffusion characteristics such as impurity diffusion concentration and diffusion depth. For example, a diffusion layer having a surface impurity concentration of 10 ¹⁹ to ²¹ can be formed by heating and diffusing at 800 ° C. or higher and 1200 ° C. or lower for 1 to 120 minutes.

The diffusion atmosphere is not particularly limited, and may be carried out in the atmosphere, or the amount of oxygen in the atmosphere may be appropriately controlled by using an inert gas such as nitrogen or argon. From the viewpoint of shortening the diffusion time, it is preferable to reduce the oxygen concentration in the atmosphere to 3% or less. Further, if necessary, firing may be carried out in the range of 200 ° C. to 850 ° C. before diffusion.

Next, as shown in FIG. 1 (c), the p-type impurity diffusion composition film 12 formed on the surface of the semiconductor substrate 11 is removed by a known etching method.

The material used for etching is not particularly limited, but for example, an etching component containing at least one of hydrogen fluoride, ammonium, phosphoric acid, sulfuric acid, and nitric acid, and other components containing water, an organic solvent, or the like. preferable. By the above steps, a p-type impurity diffusion layer can be formed on the semiconductor substrate.

In the above example, the case where the p-type impurity diffusion composition film is used to form the p-type impurity diffusion composition film has been described, but the present embodiment is not limited to this, and the n-type impurity diffusion composition film is not limited to this. Of course, it can also be applied to the case of forming an n-type impurity diffusion layer by utilizing.

Subsequently, a method for manufacturing a solar cell using the method for manufacturing a semiconductor element according to an example of the first embodiment of the present invention will be described with reference to FIG. 1D. The solar cell obtained in one example of this embodiment is a single-sided power generation type solar cell.

First, as shown in FIG. 1D, a passivation layer 16 is formed on the front surface and a passivation layer 17 is formed on the back surface.

Known materials can be used as the passivation layer. These layers may be a single layer or a plurality of layers. For example, there is a laminated layer of a thermal oxide layer, an aluminum oxide layer, a SiNx layer, and an amorphous silicon layer.

The aluminum oxide layer is particularly preferable as the passivation layer on the side of the passivation layer 17. This also serves as an electrode.

These passivation layers can be formed by a vapor deposition method such as a plasma CVD method or an ALD (atomic layer deposition) method, or a coating method.

In one example of this embodiment, the passivation layer 16 is formed in a part of the light receiving surface, and the passivation layer 17 is formed on the entire back surface.

After that, as shown in FIG. 1 (e), the contact electrode 18 is formed on the portion of the light receiving surface where the passivation layer 16 does not exist.

The electrode can be formed by applying a paste for forming an electrode and then heat-treating it.

As a result, the single-sided power generation type solar cell 10 is obtained.

(Second Embodiment)
FIG. 2A shows an example of a second embodiment of the method for manufacturing a semiconductor device of the present invention. First, as shown in FIG. 2A (a), the n-type impurity diffusion composition film 24 is patterned on the semiconductor substrate 21.

Examples of the method for forming the n-type impurity diffusion composition film include a screen printing method, an inkjet printing method, a slit coating method, a spray coating method, a letterpress printing method, and an intaglio printing method.

After forming the coating film by these methods, it is preferable to dry the n-type impurity diffusion composition film in a hot plate, an oven or the like in the range of 50 to 200 ° C. for 30 seconds to 30 minutes.

The film thickness of the n-type impurity diffusion composition film after drying is preferably 200 nm or more in consideration of masking property against p-type impurities, and preferably 5 μm or less from the viewpoint of crack resistance.

Next, as shown in FIG. 2A (b), the p-type impurity diffusion composition film 22 is formed using the n-type impurity diffusion composition film 24 as a mask.

In this case, as shown in FIG. 2A (b), the p-type impurity diffusion composition film may be formed on the entire surface, or may be formed only on the portion where the n-type impurity diffusion composition film is absent. Further, a part of the p-type impurity diffusion composition may be applied so as to overlap the n-type impurity diffusion composition film.

Examples of the method for applying the p-type impurity diffusion composition include a spin coating method, a screen printing method, an inkjet printing method, a slit coating method, a spray coating method, a letterpress printing method, and an intaglio printing method.

After forming the coating film by these methods, it is preferable to dry the p-type impurity diffusion composition film on a hot plate, an oven or the like in the range of 50 to 200 ° C. for 30 seconds to 30 minutes. The film thickness of the p-type impurity diffusion composition film after drying is preferably 100 nm or more from the viewpoint of diffusivity of p-type impurities, and preferably 3 μm or less from the viewpoint of the residue after etching.

Subsequently, as shown in FIG. 2A (c), the n-type impurity diffusion component in the n-type impurity diffusion composition film 24 and the p-type impurity diffusion component in the p-type impurity diffusion composition film 22 are simultaneously semiconductored. It is diffused in the substrate 21 to form an n-type impurity diffusion layer 25 and a p-type impurity diffusion layer 23.

Examples of the coating method, firing method, and diffusion method of the impurity diffusion composition include the same methods as described above.

Next, as shown in FIG. 2A (d), the n-type impurity diffusion composition film 24 and the p-type impurity diffusion composition film 22 formed on the surface of the semiconductor substrate 21 are removed by a known etching method.

Through the above steps, n-type and p-type impurity diffusion layers can be formed on the semiconductor substrate. By adopting such a process, the process can be further simplified as compared with the conventional method.

Here, an example in which the p-type impurity diffusion composition is applied after the n-type impurity diffusion composition is applied, but the n-type impurity diffusion composition is applied after the p-type impurity diffusion composition is applied. It is also possible to do. That is, in FIG. 2A (a), the p-type impurity diffusion composition is applied instead of the n-type impurity diffusion composition, and in FIG. 2A (b), the p-type impurity diffusion composition is applied and diffused. It is also possible to apply the n-type impurity diffusion composition.

Subsequently, with reference to FIG. 2B, a method for manufacturing a solar cell using the method for manufacturing a semiconductor element according to an example of the second embodiment of the present invention will be described. The solar cell obtained in one example of this embodiment is a back surface bonded solar cell.

First, as shown in FIG. 2B (e), a protective film 26 is formed on the entire back surface of the semiconductor substrate 21 having the n-type impurity diffusion layer 25 and the p-type impurity diffusion layer 23 formed on the back surface. Next, as shown in FIG. 3 (f), the protective film 26 is patterned by an etching method or the like to form the protective film opening 26a.

Further, as shown in FIG. 2B (g), the n-type contact electrode 29 and the p-type contact are formed by applying a pattern of the electrode paste to the region including the opening 26a and firing it by a stripe coating method or a screen printing method. The electrode 28 is formed. As a result, the back surface bonded type solar cell 20 is obtained.

(Third Embodiment)
FIG. 3A shows an example of a third embodiment of the method for manufacturing a semiconductor device of the present invention.

First, as shown in FIG. 3A (a), a p-type impurity diffusion composition film 32 is formed on the semiconductor substrate 31 using the p-type impurity diffusion composition of the present invention. Next, as shown in FIG. 3A (b), the n-type impurity diffusion composition film 34 is formed on the surface of the semiconductor substrate 31 opposite to the surface on which the p-type impurity diffusion composition film 32 is formed.

Next, as shown in FIG. 3A (c), the p-type impurity diffusion composition film 32 and the n-type impurity diffusion composition film 34 are simultaneously diffused into the semiconductor substrate 31, and the p-type impurity diffusion layer 33 and the n-type are diffused simultaneously. The impurity diffusion layer 35 is formed.

Examples of the coating method, firing method, and diffusion method of the impurity diffusion composition include the same methods as described above.

Next, as shown in FIG. 3A (d), the p-type impurity diffusion composition film 32 and the n-type impurity diffusion composition film 34 formed on the surface of the semiconductor substrate 31 are removed by a known etching method.

Through the above steps, n-type and p-type impurity diffusion layers can be formed on the semiconductor substrate. By adopting such a process, the process can be simplified as compared with the conventional method.

Here, an example in which the n-type impurity diffusion composition is applied after the p-type impurity diffusion composition is applied, but the p-type impurity diffusion composition is applied after the n-type impurity diffusion composition is applied. Is also possible.

Subsequently, with reference to FIG. 3B, a method for manufacturing a solar cell using the method for manufacturing a semiconductor element according to an example of the third embodiment of the present invention will be described. The solar cell obtained in one example of this embodiment is a double-sided power generation type solar cell.

First, as shown in FIG. 3B (e), passivation layers 36 are formed on the light receiving surface and the back surface, respectively.

The materials used for the passivation layer, the structure of the layer, and the method of forming the layer are the same as those in the first embodiment.

In one example of this embodiment, the passivation layer 36 is formed in a part of the light receiving surface and the back surface.

After that, as shown in FIG. 3B (f), a p-type contact electrode 38 and an n-type contact electrode 39 are formed on the light receiving surface and the back surface, respectively, in a portion where the passivation layer 36 does not exist.

The electrode can be formed by applying a paste for forming an electrode and then heat-treating it.

As a result, the double-sided power generation type solar cell 30 can be obtained.

(Fourth Embodiment)
FIG. 4 shows an example of a fourth embodiment of the method for manufacturing a semiconductor device of the present invention.

((A) step)
As shown in FIG. 4A, the first conductive type impurity diffusion composition is applied to one surface of the semiconductor substrate 41 to form the first conductive type impurity diffusion composition film 42.

In the following description, the first conductive type will be described as p type, and the second conductive type will be described as n type. That is, the first conductive type impurity diffusion composition film is a p-type impurity diffusion composition film. Of course, the first conductive type and the second conductive type may be reversed.

In FIG. 4A, a mode in which the p-type impurity diffusion composition is applied to the entire surface of one surface of the semiconductor substrate has been described, but the p-type impurity diffusion composition may be partially applied. Examples of the method for applying the impurity diffusion composition and the method for firing include the same methods as described above.

(Step (b))
As shown in (b) -1 of FIG. 4, the semiconductor substrates 41 having the p-type impurity diffusion composition film 42 formed on one surface thereof are formed in pairs, and each p-type impurity diffusion composition film 42 is formed. Are placed on the diffusion board 110 with the surfaces on which they are formed facing each other.

The diffusion board has a groove for arranging the semiconductor substrate. There are no particular restrictions on the size and pitch of the grooves on the diffusion board. The diffusion board may be tilted with respect to the horizontal direction. The material of the diffusion board is not particularly limited as long as it can withstand the diffusion temperature, but quartz is preferable.

Next, as shown in FIG. 4B-2, the diffusion board 110 on which the semiconductor substrate 41 is arranged is heated in the diffusion furnace 100 to diffuse the p-type impurities into the semiconductor substrate 41 to diffuse the p-type impurities. The impurity diffusion layer 43 is formed.

At this time, since the pair of semiconductor substrates is arranged as described above, even if the p-type impurities diffuse into the air from the p-type impurity diffusion composition membrane, it is the p-type impurity diffusion composition membrane of the semiconductor substrate. It is difficult to reach the surface opposite to the surface on which the is formed. Therefore, it is possible to suppress so-called outdiffusion in which impurities are diffused to a place different from the target place in the semiconductor substrate. Examples of the diffusion method of the impurity diffusion composition include the same methods as described above.

Further, before the step (b), for example, a semiconductor substrate having a p-type impurity diffusion composition film formed on one surface is heated at a temperature equal to or lower than the heat treatment temperature at the time of diffusion and in an atmosphere containing oxygen. It is preferable to remove at least a part of organic components such as a binder resin in the film of the p-type impurity diffusion composition by the treatment. By removing at least a part of organic components such as binder resin in the p-type impurity diffusion composition film, the concentration of impurity components in the p-type impurity diffusion composition film on the semiconductor substrate can be increased. The diffusivity of p-type impurities is likely to improve.

(Step (c))
In the step (c), the semiconductor substrate is heated while flowing a gas containing n-type impurities to form the n-type impurity diffusion layer 45.

Examples of the gas containing n-type impurities include POCl ₃ gas and the like. For example POCl ₃ gas and bubbling _{N 2} gas or nitrogen / oxygen mixed gas to the _{POCl 3} solution, can be obtained by heating the POCl ₃ solution. When the second conductive type is p type, gas such as BBr ₃ and BCl ₃ can be mentioned.

The heating temperature is preferably 750 ° C. to 1050 ° C., more preferably 800 ° C. to 1000 ° C.

The gas atmosphere is not particularly limited, but is preferably a mixed gas atmosphere of nitrogen, oxygen, argon, helium, xenone, neon, krypton, etc., more preferably a mixed gas of nitrogen and oxygen, and contains oxygen. A mixed gas of nitrogen and oxygen having a ratio of 5% by volume or less is particularly preferable.

Further, since the process time for changing the gas atmosphere can be shortened, it is preferable to perform the step (c) in the same gas atmosphere as the step (b). In particular, it is preferable that the ratio of nitrogen and oxygen in the gas atmosphere in the step (b) is the same as the ratio of nitrogen and oxygen in the gas atmosphere in the step (c). The preferred ratio in this case is oxygen: nitrogen = 1: 99 to 5:95 in volume ratio.

After the step (b), the heat-treated product layer of the p-type impurity diffusion composition film remains on the upper part of the p-type impurity diffusion layer. It is preferable to carry out the step (c) using this as a mask for a gas containing n-type impurities. By doing so, it is possible to suppress the mixing of n-type impurities into the p-type impurity diffusion layer.

Either the step (b) or the step (c) may be performed first, and the step (c) may be performed at the same time as the step (b). When the heat-treated material layer of the p-type impurity diffusion composition film is used as a mask, it is preferable that the step (c) is performed after the step (b).

Further, it is more preferable that the step (c) is continuously performed after the step (b). For example, after the step (b), it is preferable to move to the step (c) as it is without removing the diffusion board from the firing furnace. To continuously perform the step (c) after the step (b) means to carry out the step (c) after the step (b).

The heating temperature for forming the n-type impurity diffusion layer in the step (c) is 50 to 200 ° C. higher than the heating temperature for forming the p-type impurity diffusion layer in the step (b). A low temperature is preferred. The heating temperature when the n-type impurity diffusion layer is formed in the step (c) is set to a temperature 50 to 200 ° C. lower than the heating temperature when the p-type impurity diffusion layer is formed in the step (b). Therefore, when the step (c) is continuously performed after the step (b), the influence of heating on the p-type impurity diffusion layer formed in the step (b) can be minimized. It becomes easier to control the impurity diffusion of the mold.

In the step (c), the first conductive type is p-type because the heating temperature can be lower when diffusing with a gas containing n-type impurities than when diffusing with a gas containing p-type impurities. , The second conductive type is preferably n type.

<Manufacturing method of solar cell element>
The method for manufacturing a solar cell of the present invention includes the method for manufacturing a semiconductor element of the present invention, and specifically, the first conductive type impurity diffusion layer and the second conductive type obtained in the above steps. It has a step of forming an electrode on each impurity diffusion layer of a semiconductor substrate on which an impurity diffusion layer is formed. The details will be described by exemplifying a single-sided power generation type solar cell in FIG. 1, a backside bonded type solar cell in FIG. 2, and a double-sided power generation type solar cell in FIG.

The method for manufacturing a semiconductor element and the method for manufacturing a solar cell of the present invention are not limited to the above-described embodiments, and various modifications such as design changes can be made based on the knowledge of those skilled in the art. The embodiment to which such a modification is added is also included in the scope of the present invention.

The impurity diffusion composition of the present invention is also applied to photovoltaic devices such as solar cells and semiconductor devices that form an impurity diffusion region on the semiconductor surface, for example, transistor arrays, diode arrays, photodiode arrays, and transducers. can do.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Of the compounds used, those using abbreviations are shown below.

GBL: γ-Butyrolactone PGMEA: Propylene Glycol Monomethyl Ether Acetate PVA: Polyvinyl Alcohol TMSOX: Trimethoxysilyl Oxetane (manufactured by Toa Synthetic Co., Ltd.)
PhTMS: Phenyltrimethoxysilane OXE-10: (3-ethyloxetane-3-yl) methyl acrylate.

(1) Solution viscosity, TI value, storage stability For the impurity diffusion composition with a viscosity of less than 1,000 mPa · s, use a rotary viscometer TVE-25L (E-type digital viscometer) manufactured by Toki Sangyo Co., Ltd. The viscosity was measured at a temperature of 25 ° C. and a rotation speed of 20 rpm. Further, for the impurity diffusion composition having a viscosity of 1,000 mPa · s or more, the viscosity at a liquid temperature of 25 ° C. and a rotation speed of 20 rpm was measured using RVDV-11 + P (B-type digital viscometer) manufactured by Brookfield. Here, the viscosities at the rotation speeds of 2 rpm and 20 rpm were measured, and the ratio of the viscosity at the rotation speed of 2 rpm to the viscosity at the rotation speed of 20 rpm was taken as the TI value. Further, the viscosity immediately after the preparation of the impurity diffusion composition and the viscosity after storage at 25 ° C. for 7 days after the preparation were measured and used as an index of storage stability. Those having a viscosity increase rate of 5% or less were judged to be excellent (A), those exceeding 5% and within 10% were judged to be good (B), and those exceeding 10% were judged to be bad (C).

(2) Evaluation of peelability An n-type silicon wafer (manufactured by Fellow Tech Silicon Co., Ltd., surface resistivity 410Ω / □) cut into 3 cm x 3 cm was immersed in a 1% hydrofluoric acid aqueous solution for 1 minute, washed with water, and then hot after air blowing. The plate was treated at 140 ° C. for 5 minutes.

The impurity diffusion composition to be measured was applied to the silicon wafer by a known coating method so that the prebake film thickness was about 500 nm. After coating, the silicon wafer was prebaked at 140 ° C. for 5 minutes.

Subsequently, each silicon wafer was placed in an electric furnace and maintained at 900 ° C. for 30 minutes in an atmosphere of nitrogen: oxygen = 99: 1 (volume ratio) to thermally diffuse impurities.

Each silicon wafer after thermal diffusion was immersed in a 5 wt% hydrofluoric acid aqueous solution at 23 ° C. for 1 minute to peel off the diffusing agent and the mask. After peeling, the silicon wafer was immersed in pure water for cleaning, and the presence or absence of residue was visually observed on the surface. After soaking for 1 minute, surface deposits can be visually confirmed, but those that can be removed by rubbing with a waste cloth are bad (C), and those that exceed 30 seconds and the surface deposits cannot be visually confirmed within 1 minute are good (B). ), Those whose surface deposits could not be visually confirmed within 30 seconds were designated as excellent (A). From the viewpoint of production tact, good (B) can be used, but excellent (A) is preferable.

(3) Sheet resistance value measurement For the silicon wafer after impurity diffusion used for peelability evaluation, p / n judgment is performed using a p / n judgment machine, and the surface resistance is determined by the four-probe type surface resistance measurement device RT-. It was measured using 70V (manufactured by Napson Corporation) and used as the sheet resistance value. The sheet resistance value is an index of impurity diffusivity, and the smaller the resistance value, the larger the amount of impurity diffusivity.

(4) Diffusion Uniformity The surface concentration distribution of impurities was measured on the silicon wafer after diffusion of impurities used for measuring the sheet resistance value using a secondary ion mass analyzer IMS7f (manufactured by Camera). From the obtained surface concentration distribution, read the surface concentrations of 10 points at 100 μm intervals, calculate the "standard deviation / average" which is the ratio of the average and the standard deviation, and the "standard deviation / average" is 0.3 or less. The variation in the surface concentration of impurities, which was judged to be excellent (A), those exceeding 0.3 and 0.6 or less as good (B), and those exceeding 0.6 as bad (C), greatly affected the power generation efficiency. Therefore, it is most preferably excellent (A).

(5) Barrier property An n-type silicon wafer (manufactured by Fellow Tech Silicon Co., Ltd., surface resistivity 410Ω / □) cut into 3 cm x 3 cm is immersed in a 1% hydrofluoric acid aqueous solution for 1 minute, washed with water, air blown, and then a hot plate. The treatment was carried out at 140 ° C. for 5 minutes.

As shown in FIG. 5A, the p-type impurity diffusion compositions of each Example and Comparative Example were applied to the silicon wafer 51 by a known coating method so that the prebake film thickness was about 500 nm. After coating, the silicon wafer was prebaked at 140 ° C. for 5 minutes to prepare a p-type impurity diffusion composition film 52.

Next, as shown in FIG. 5 (b), the n-type impurity diffusible composition (OCD T-1, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was separately prepared by a known coating method so that the prebake film thickness was about 500 nm. Was applied to the silicon wafer 61 of. After coating, the silicon wafer was prebaked at 140 ° C. for 5 minutes to prepare an n-type impurity diffusion composition coating film 64.

Subsequently, as shown in FIG. 5C, the silicon wafer 51 on which the p-type impurity diffusion composition film 52 was formed and the silicon wafer 61 on which the n-type impurity diffusion composition film 64 was formed were formed. Impurities were placed in an electric furnace facing each other at intervals of 5 mm and maintained at 900 ° C. for 30 minutes in an atmosphere of nitrogen: oxygen = 99: 1 (volume ratio) to diffuse impurities. As a result, as shown in FIG. 5D, a p-type impurity diffusion layer 53 was formed on the silicon wafer 51, and an n-type impurity diffusion layer 65 was formed on the silicon wafer 61.

After thermal diffusion, each silicon wafer was immersed in a 5 wt% hydrofluoric acid aqueous solution at 23 ° C. for 1 minute to peel off the cured diffuser (FIG. 5 (e)).

Then, the surface concentration distribution of the phosphorus element was measured on the silicon wafer 51 using a secondary ion mass spectrometer IMS7f (manufactured by Camera). The lower the surface concentration of the phosphorus element, the higher the barrier property to the phosphorus element diffused from the facing n-type impurity diffusion composition. Surface concentration of the resulting elemental phosphorus excellent ones ^{10 17} or less (A), those of ^{10 17} to greater than ^{10 18} or less good (B), ^{10 18} to greater than ^{10 19} or less of those of not bad (C) Those exceeding 10 ¹⁹ were judged to be bad (D).

(6) Screen Printability The impurity diffusion compositions of each Example and Comparative Example were patterned in stripes by screen printing, and the stripe width accuracy was confirmed.

As a substrate, a semiconductor substrate made of n-type single crystal silicon having a side of 156 mm was prepared, and both surfaces were alkali-etched in order to remove slice damage and natural oxides. At this time, innumerable irregularities having a typical width of 40 to 100 μm and a depth of about 3 to 4 μm were formed on both sides of the semiconductor substrate, and these were used as coated substrates.

Using a screen printing machine (Microtech Co., Ltd. TM-750 type), 175 screen masks with a width of 200 μm and a length of 13.5 cm were formed at a pitch of 600 μm (SUS Co., Ltd., 400 mesh). , Wire diameter 23 μm) was used to form a striped pattern.

After screen printing the p-type impurity diffusion composition, the substrate is heated in air at 140 ° C. for 5 minutes and then at 230 ° C. for 30 minutes to obtain a thickness of about 1.5 μm, a width of about 210 μm, a pitch of 600 μm, and a length. A 13.5 cm pattern was formed.

Here, the line width is measured at 10 points at equal intervals for any one line, and the one with a standard deviation of the coating width of 12.5 μm or less is excellent (A), and the one with a coating width exceeding 12.5 μm and within 15 μm is good. (B), the one exceeding 15 μm and within 17.5 μm was judged as bad (C), and the one exceeding 17.5 μm and within 20 μm was judged as worst (D).

(7) Continuous screen printability When the above screen printability evaluation was performed continuously for 10 sheets, those in which coating defects such as bleeding and blurring did not occur were rated as good, and those in which they did occur were rated as bad.

Example 1
(1) (A) Synthesis of polymer 55.64 g (0.2 mol) of TMSOX and 67.75 g of GBL were charged in a 500 mL three-necked flask, and 0.11 g of sulfuric acid was dissolved in 18 g of water while stirring at 40 ° C. Was added over 30 minutes. After completion of the dropping, the mixture was stirred at 40 ° C. for 1 hour, then heated to 70 ° C. and stirred for 30 minutes. Then, the temperature of the oil bath was raised to 115 ° C. The internal temperature of the solution reached 100 ° C. 1 hour after the start of temperature rise, and the mixture was heated and stirred for 1 hour (internal temperature was 100 to 110 ° C.). The obtained solution was cooled in an ice bath to obtain a polysiloxane (TMSOX (100)) solution. The solid content concentration of the polysiloxane solution was 40.0% by weight.

(2) Preparation of Impurity Diffusion Composition 12.54 g of the polysiloxane synthesized above, 1.26 g of boric acid, and 81.6 g of GBL are mixed, and BYK-333 is added so as to be 300 ppm with respect to the entire solution. And it was stirred well so that it became uniform. The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, the diffusion uniformity, and the barrier property were measured using the obtained solution, they were all good as shown in Table 2.

Example 2
(1) (A) Synthesis of polymer 55.64 g (0.2 mol) of TMSOX, 39.658 g (0.2 mol) of KBM-103 (phenyltrimethoxysilane), and 163.2 g of GBL were charged in a 500 mL three-necked flask. A sulfuric acid aqueous solution prepared by dissolving 0.22 g of sulfuric acid in 36 g of water was added over 30 minutes with stirring at 40 ° C. After completion of the dropping, the mixture was stirred at 40 ° C. for 1 hour, then heated to 70 ° C. and stirred for 30 minutes. Then, the temperature of the oil bath was raised to 115 ° C. The internal temperature of the solution reached 100 ° C. 1 hour after the start of temperature rise, and the mixture was heated and stirred for 1 hour (internal temperature was 100 to 110 ° C.). The obtained solution was cooled in an ice bath to obtain a polysiloxane (TMSOX (50) / PhTMS (50)) solution. The solid content concentration of the polysiloxane solution was 40.3% by weight.

(2) Preparation of Impurity Diffusion Composition 12.54 g of the polysiloxane synthesized above, 1.26 g of boric acid, and 81.6 g of GBL are mixed, and BYK-333 is added so as to be 300 ppm with respect to the entire solution. And it was stirred well so that it became uniform. The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, the diffusion uniformity, and the barrier property were measured using the obtained solution, they were all good as shown in Table 2.

Example 3
An impurity diffusion composition was obtained in the same manner as in Example 2 except that the composition of the polysiloxane was (TMSOX (5) / PhTMS (95)). The solid content concentration of the polysiloxane solution was 40.6% by weight. When the viscosity, TI value, storage stability, peelability, sheet resistance value, diffusion uniformity, and barrier property were measured using the obtained impurity diffusion composition, all were good as shown in Table 2. ..

Example 4
An impurity diffusion composition was obtained in the same manner as in Example 2 except that the composition of the polysiloxane was (TMSOX (95) / PhTMS (5)). The solid content concentration of the polysiloxane solution was 40.0% by weight. When the viscosity, TI value, storage stability, peelability, sheet resistance value, diffusion uniformity, and barrier property were measured using the obtained impurity diffusion composition, all were good as shown in Table 2. ..

Example 5
(1) Synthesis of Polymer (A) 18.2 g of propylene glycol monomethyl ether acetate was introduced into a 500 mL three-necked flask and the temperature was raised to 100 ° C. Then, a mixed solution of 5.1 g of OXE-10, 2.1 g of acrylic acid, 0.36 g of azobisisobutyronitrile, and 13.60 g of propylene glycol monomethyl ether acetate was added dropwise to the flask over 2 hours from the dropping funnel. Then, stirring was continued at 100 ° C. for another 10 hours. The obtained solution was cooled to obtain an acrylic (OXE-10 (50) / acrylic acid (50)) solution.

(2) Preparation of Impurity Diffusion Composition 12.54 g of the acrylic solution synthesized above, 1.26 g of boric acid and 81.6 g of GBL are mixed, and BYK-333 is added so as to be 300 ppm with respect to the entire solution. And stirred well so that it became uniform. The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, and the diffusion uniformity were measured using the obtained solution, all were good as shown in Table 2.

Example 6
The thickeners shown in Table 1 were added to the impurity diffusion composition prepared in Example 1 so as to have a predetermined weight% concentration with respect to the entire solution, and the rotation / revolution mixer ARE-310 (Shinky Co., Ltd.) (Manufactured) was dissolved (stirring: 15 minutes, defoaming: 1 minute). The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, the diffusion uniformity, the barrier property, the screen printability, and the screen continuous printability were measured using the obtained solution, all were good as shown in Table 2.

Example 7
The thickeners shown in Table 1 are added to the impurity diffusion composition prepared in Example 2 so as to have a predetermined weight% concentration with respect to the entire solution, and the rotation / revolution mixer ARE-310 (Shinky Co., Ltd.) (Manufactured) was dissolved (stirring: 15 minutes, defoaming: 1 minute). The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, the diffusion uniformity, the barrier property, the screen printability, and the screen continuous printability were measured using the obtained solution, all were good as shown in Table 2.

Example 8
To the impurity diffusion composition prepared in Example 3, the thickeners shown in Table 1 were added so as to have a predetermined weight% concentration with respect to the entire solution, and the rotation / revolution mixer ARE-310 (Shinky Co., Ltd.) (Manufactured) was dissolved (stirring: 15 minutes, defoaming: 1 minute). The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, the diffusion uniformity, the barrier property, the screen printability, and the screen continuous printability were measured using the obtained solution, all were good as shown in Table 2.

Example 9
To the impurity diffusion composition prepared in Example 4, the thickeners shown in Table 1 were added so as to have a predetermined weight% concentration with respect to the entire solution, and the rotation / revolution mixer ARE-310 (Shinky Co., Ltd.) (Manufactured) was dissolved (stirring: 15 minutes, defoaming: 1 minute). The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, the diffusion uniformity, the barrier property, the screen printability, and the screen continuous printability were measured using the obtained solution, all were good as shown in Table 2.

Example 10
To the impurity diffusion composition prepared in Example 5, the thickeners shown in Table 1 were added so as to have a predetermined weight% concentration with respect to the entire solution, and the rotation / revolution mixer ARE-310 (Shinky Co., Ltd.) (Manufactured) was dissolved (stirring: 15 minutes, defoaming: 1 minute). The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, the diffusion uniformity, the barrier property, the screen printability, and the screen continuous printability were measured using the obtained solution, all were good as shown in Table 2.

Example 11
An impurity diffusion composition was obtained in the same manner as in Example 2 except that the composition of the polysiloxane was (TMSOX (10) / PhTMS (90)). The solid content concentration of the polysiloxane solution was 40.0% by weight. When the viscosity, TI value, storage stability, peelability, sheet resistance value, diffusion uniformity, and barrier property were measured using the obtained impurity diffusion composition, all were good as shown in Table 2. ..

Example 12
An impurity diffusion composition was obtained in the same manner as in Example 2 except that the composition of the polysiloxane was (TMSOX (90) / PhTMS (10)). The solid content concentration of the polysiloxane solution was 40.2% by weight. When the viscosity, TI value, storage stability, peelability, sheet resistance value, diffusion uniformity, and barrier property were measured using the obtained impurity diffusion composition, all were good as shown in Table 2. ..

Example 13
To the impurity diffusion composition prepared in Example 11, the thickeners shown in Table 1 were added so as to have a predetermined weight% concentration with respect to the entire solution, and the rotation / revolution mixer ARE-310 (Shinky Co., Ltd.) (Manufactured) was dissolved (stirring: 15 minutes, defoaming: 1 minute). The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, the diffusion uniformity, the barrier property, the screen printability, and the screen continuous printability were measured using the obtained solution, all were good as shown in Table 2.

Example 14
The thickeners shown in Table 1 are added to the impurity diffusion composition prepared in Example 12 so as to have a predetermined weight% concentration with respect to the entire solution, and the rotation / revolution mixer ARE-310 (Shinky Co., Ltd.) (Manufactured) was dissolved (stirring: 15 minutes, defoaming: 1 minute). The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Moreover, when the peelability, the sheet resistance value, the diffusion uniformity, the barrier property, the screen printability, and the screen continuous printability were measured using the obtained solution, all were good as shown in Table 2.

Comparative Example 1
20.8 g of PVA (manufactured by Wako Pure Chemical Industries, Ltd., degree of polymerization 500) and 144 g of water were charged in a 500 mL three-necked flask, the temperature was raised to 80 ° C. with stirring, and the mixture was stirred for 1 hour. Then, 231.6 g of GBL and 3.6 g of boric acid were added, and the mixture was stirred at 80 ° C. for 1 hour. After cooling to 40 ° C., BYK-333 was added so as to be 300 ppm with respect to the whole solution, and the mixture was sufficiently stirred to be uniform to obtain an impurity diffusion composition. Then, the thickeners shown in Table 1 were added so as to have a predetermined weight% concentration with respect to the whole solution, and dissolved using a rotation / revolution mixer ARE-310 (manufactured by Shinky Co., Ltd.) (stirring). : 15 minutes, defoaming: 1 minute). The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. When the peelability, sheet resistance value, diffusion uniformity, barrier property, screen printability, and screen continuous printability were measured using the obtained solution, as shown in Table 2, storage stability, barrier property, and screen were measured. The result was inferior in continuous printability.

Comparative Example 2
20.8 g of trimethylolpropane, 231.6 g of GBL, and 3.6 g of boric acid were placed in a 500 mL three-necked flask, and the mixture was stirred at 80 ° C. for 1 hour. After cooling to 40 ° C., BYK-333 was added so as to be 300 ppm with respect to the whole solution, and the mixture was sufficiently stirred to be uniform to obtain an impurity diffusion composition. Then, the thickeners shown in Table 1 were added so as to have a predetermined weight% concentration with respect to the whole solution, and dissolved using a rotation / revolution mixer ARE-310 (manufactured by Shinky Co., Ltd.) (stirring). : 15 minutes, defoaming: 1 minute). The viscosities, TI values, and storage stability of the obtained solutions are the results shown in Table 2. Further, when the peelability, sheet resistance value, diffusion uniformity, barrier property, screen printability, and screen continuous printability were measured using the obtained solution, as shown in Table 2, the diffusion uniformity and barrier property were inferior. The result was.

10, 20, 30, 40 Solar cells 11, 21, 31, 41 Semiconductor substrates 12, 22, 32, 42, 52 p-type impurity diffusion composition film 13, 23, 33, 43, 53 p-type impurity diffusion layer 14, 24, 34, 64 n-type impurity diffusion composition film 15, 25, 35, 45, 65 n-type impurity diffusion layer 16, 17, 36 Passion layer 18, 28, 29, 38, 39 Contact electrode 26 Protective film 26a Opening 51 , 61 Silicon Wafer
100 Diffusion furnace 110 Diffusion board

Claims (11)

(A) A polymer containing at least one structure selected from the following general formulas (1) and (2) in the side chain (hereinafter referred to as (A) polymer), and (B) Impurity diffusion containing an impurity diffusion component. Composition.

(In the general formulas (1) and (2), R ^{1 to} R ¹⁴ independently represent a hydrogen atom or an organic group having 1 to 8 carbon atoms. A ₁ represents an integer of ₁ to 4, and a ₂ and _{a 3} each independently represent an integer of 0 to 2 _.a 2 + _{a 3} represents an integer of 0-3. * indicates the union of the polymer.) The impurity diffusion composition according to claim 1, wherein the polymer (A) is a polymer composed of siloxane or acrylic. The polymer (A) has at least one partial structure represented by any of the following general formulas (3) and (4) and a partial structure represented by any of the following general formulas (5) and (6). The impurity diffusion composition according to claim 1, which is a polymer composed of a siloxane containing more than one species.

(R ¹⁵ represents an alkylene group having 1 to 8 carbon atoms. R ¹⁶ is a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, and 2 carbon atoms. Indicates any of the acyloxy groups of ~ 6. R ¹⁷ and R ¹⁸ are hydroxyl groups, alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, alkenyl groups having 2 to 10 carbon atoms, and 2 to 2 carbon atoms. It represents either an acyl group of 6 or an aryl group having 6 to 15 carbon atoms. X represents at least one structure selected from the general formulas (1) and (2), and the general formula in the siloxane structure. The proportion of the partial structure shown in any of (3) and (4) is less than 5 to 100 mol%.) The polymer (A) has a partial structure represented by any of the following general formulas (3) and (4) and a partial structure represented by any of the following general formulas (5) and (6), and R ¹⁷ The impurity diffusion composition according to claim 3, wherein is an aryl group having 6 to 15 carbon atoms, and the proportion of the partial structure represented by any of the general formulas (5) and (6) is 5 to 95 mol%. The impurity diffusion composition according to claim 1, wherein the polymer (A) is a polymer composed of an acrylic containing a partial structure represented by the following general formula (7) and a partial structure represented by the following general formula (8). ..

(R ¹⁹ and R ²¹ each independently represent a hydrogen atom, a halogen, an alkyl group having 1 to 4 carbon atoms or a fluoroalkyl group having 1 to 4 carbon atoms. R ²⁰ has 1 to 8 carbon atoms. R ²² represents an alkyl group having 1 to 4 carbon atoms. X represents at least one structure selected from the general formulas (1) and (2). A ₄ and a ₅ represent 0. or 1 represents an integer, at least one of a ₄ and a ₅ 1. in general moiety ratio structure occupied represented by (7) in the polymer comprising the acrylic is less than 5 to 100 mol% .) (B) The impurity diffusion composition according to any one of claims 1 to 5, wherein the impurity diffusion component is a boron compound. A step of applying the impurity diffusion composition according to any one of claims 1 to 6 to a semiconductor substrate to form an impure diffusion composition film, and a step of diffusing impurities from the impurity diffusion composition film to diffuse impurities to the semiconductor substrate. A method for manufacturing a semiconductor device, which includes a step of forming a layer. The step of applying the n-type impurity diffusion composition to a semiconductor substrate to form an n-type impurity diffusion composition film, and after the step, the impurity diffusion composition according to claim 6, which is a p-type impurity diffusion composition, is applied to the semiconductor. Includes a step of applying to a substrate to form a p-type impurity diffusion composition film and a step of simultaneously forming an n-type impurity diffusion layer and a p-type impurity diffusion layer on the semiconductor substrate by heating the semiconductor substrate. A method for manufacturing a semiconductor element. The step of applying the impurity diffusion composition according to claim 6, which is a p-type impurity diffusion composition, to one surface of the semiconductor substrate to form a p-type impurity diffusion composition film, and on the other surface of the semiconductor substrate. , N-type impurity diffusion composition is applied to form an n-type impurity diffusion composition film, and by heating the semiconductor substrate, a p-type impurity diffusion layer and an n-type impurity diffusion layer are simultaneously formed on the semiconductor substrate. A method for manufacturing a semiconductor device, which includes a step of forming. A method for manufacturing a semiconductor element using a plurality of semiconductor substrates, which includes the following steps (a) to (c), and in the steps (b) and (c), a set of two semiconductor substrates is used. A method for manufacturing a semiconductor device, in which the surfaces on which the first conductive type impurity diffusion composition film is formed are arranged so as to face each other.
(A) A step of applying the impurity diffusion composition according to any one of claims 1 to 6 to one surface of each semiconductor substrate to form a first conductive type impurity diffusion composition film.
(B) The semiconductor substrate on which the first conductive type impurity diffusion composition film is formed is heated to diffuse the first conductive type impurities into the semiconductor substrate to form a first conductive type impurity diffusion layer. The process of forming.
(C) The semiconductor substrate is heated in an atmosphere having a gas containing the second conductive type impurities to diffuse the second conductive type impurities on the other surface of the semiconductor substrate to diffuse the second conductive type impurities. The process of forming a diffusion layer. A method for manufacturing a solar cell, which comprises the method for manufacturing a semiconductor element according to any one of claims 7 to 10.

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