WO2013111840A1

WO2013111840A1 - Coating liquid for forming diffusion prevention layer, method for producing semiconductor substrate with dopant diffusion layer using same, and method for manufacturing solar cell

Info

Publication number: WO2013111840A1
Application number: PCT/JP2013/051529
Authority: WO
Inventors: 勝間　勝彦; 佐藤　弘章; 加藤　邦泰; 由佳堤
Original assignee: 日本合成化学工業株式会社
Priority date: 2012-01-26
Filing date: 2013-01-25
Publication date: 2013-08-01
Also published as: TW201341453A; JP5567163B2; JP2014116572A

Abstract

A coating liquid for forming diffusion prevention layers, which is applied to the surface of a semiconductor substrate for the purpose of preventing diffusion of a dopant, and which contains a polyvinyl alcohol resin (component (A)) and fine metal oxide particles (component (B)). Consequently, there can be provided: a coating liquid for forming diffusion prevention layers, which is highly uniform in diffusion prevention performance and has excellent coating film formability by screen printing or the like; a method for producing a semiconductor substrate with a dopant diffusion layer, said method using the coating liquid for forming diffusion prevention layers; and a method for manufacturing a solar cell.

Description

Coating solution for forming diffusion preventing layer, method for producing semiconductor substrate with dopant diffusion layer using the same, and method for producing solar cell

The present invention relates to a coating solution for forming an anti-diffusion layer that is applied to the surface of a semiconductor substrate to prevent dopant diffusion, a method for producing a semiconductor substrate with a dopant diffusion layer using the same, and a method for producing a solar cell. .

A pn junction solar cell has a structure in which a p-type semiconductor and an n-type semiconductor are joined.
Then, photoelectrons are generated by the light striking the joint surface (internal photoelectric effect), and the photoelectrons move in a certain direction due to the rectifying action of the semiconductor. ) Can be obtained.

As a method of forming the pn junction structure as described above on a semiconductor substrate, for example, a dopant (impurity) such as phosphorus or boron is diffused on one surface of the semiconductor substrate, and a p-type or n-type semiconductor is used depending on the type of the dopant. A method for forming a layer (dopant diffusion layer) is widely used.

Then, when forming the dopant diffusion layer on the semiconductor substrate as described above, in order to prevent the diffusion of the dopant to other than the desired location, a diffusion prevention layer is formed on the semiconductor substrate surface in advance, and after the diffusion of the dopant A technique of removing the diffusion preventing layer has been studied.

For example, the diffusion prevention layer can be formed by printing an organic solvent-based solution containing metal oxide fine particles such as titanium oxide and aluminum oxide by screen printing or the like, or by spin coating or the like. (See Patent Documents 1 and 2).

JP-A-7-221333 JP 2003-158277 A

However, the organic solvent-based anti-diffusion layer forming solution as described above has insufficient dispersibility of the metal oxide fine particles, so that the anti-diffusion layer formed thereby has poor uniformity of anti-diffusion performance. In particular, since the coating by spin coating is difficult to form a coating having a uniform thickness when performed over a wide range, the solution for forming a diffusion preventing layer having poor uniformity of the diffusion preventing performance as described above is applied to this coating method. It is unsuitable.

The present invention has been made in view of such circumstances, a coating liquid for forming an anti-diffusion layer having high uniformity of anti-diffusion performance and excellent coating film formation by screen printing, etc., and a dopant using the same The object is to provide a method for producing a semiconductor substrate with a diffusion layer and a method for producing a solar cell.

In order to achieve the above object, the present invention provides a coating solution for forming a diffusion prevention layer for preventing diffusion of a dopant by coating on the surface of a semiconductor substrate, comprising the following components (A) and (B): The coating liquid for forming the diffusion preventing layer is a first gist.
(A) Polyvinyl alcohol resin.
(B) Metal oxide fine particles.

The present invention also includes a step of coating the part of the surface of the semiconductor substrate with the coating liquid for forming the diffusion prevention layer according to the first aspect to form a diffusion prevention layer, and the surface of the semiconductor substrate with the diffusion prevention layer. A step of diffusing the dopant into the surface layer portion of the semiconductor substrate on which the diffusion prevention layer is not formed, and a step of removing the diffusion prevention layer from the semiconductor substrate on which the dopant diffusion layer is formed. The manufacturing method of the semiconductor substrate with a dopant diffusion layer provided is a second gist.

In the present invention, after the dopant diffusion solution is applied to a part of the surface of the semiconductor substrate, the diffusion-preventing layer-forming coating solution according to the first aspect is applied so as to cover the application surface, and diffusion is performed. A step of forming a prevention layer, a heat treatment, a step of diffusing the dopant in the applied dopant diffusion solution into the surface layer portion of the semiconductor substrate to form a dopant diffusion layer, and formation of the dopant diffusion layer A method for producing a semiconductor substrate with a dopant diffusion layer, comprising a step of removing a diffusion preventing layer from the semiconductor substrate thus formed, is a third gist.

Moreover, this invention is a manufacturing method of the solar cell provided with the semiconductor substrate with a dopant diffusion layer, Comprising: The manufacturing method of the solar cell which forms the said semiconductor substrate with a dopant diffusion layer by the manufacturing method of the said 2nd or 3rd summary. This is the fourth gist.

That is, the present inventors have conducted intensive research to solve the above problems. In the course of the research, the present inventors recalled a coating solution containing a polyvinyl alcohol resin (A component) together with metal oxide fine particles (B component) as a solution for forming a diffusion prevention layer. In other words, the presence of the polyvinyl alcohol resin in the coating liquid has led to excellent dispersibility of the metal oxide fine particles, and thus the uniformity of the anti-diffusion performance is increased, and the intended purpose can be achieved. The present invention has been reached.

Thus, the diffusion-preventing layer forming coating solution of the present invention contains a polyvinyl alcohol resin (component A) and metal oxide fine particles (component B). Therefore, the uniformity of the anti-diffusion performance is high, and the coating film formability by screen printing or the like is excellent. Further, the diffusion preventing layer made of the coating solution can be easily removed by washing with hydrofluoric acid (HF).

Further, a step of forming a diffusion prevention layer by applying a coating solution for forming a diffusion prevention layer on a part of the surface of the semiconductor substrate, and a diffusion of a dopant on the surface of the semiconductor substrate with the diffusion prevention layer, the diffusion prevention layer A method for producing a semiconductor substrate with a dopant diffusion layer, comprising: a step of forming a surface layer portion of a semiconductor substrate in which no dopant is formed as a dopant diffusion layer; and a step of removing the diffusion prevention layer from the semiconductor substrate on which the dopant diffusion layer is formed. When the coating solution for forming a diffusion preventing layer of the present invention containing a polyvinyl alcohol resin (component A) and fine metal oxide particles (component B) is used as the coating solution for forming the diffusion preventing layer, the portion other than the desired portion The dopant diffusion layer can be effectively formed on the semiconductor substrate while preventing the diffusion of the dopant into the semiconductor substrate.

Further, after applying the dopant diffusion solution to a part of the surface of the semiconductor substrate, applying a diffusion prevention layer forming coating solution so as to cover the coating surface, forming a diffusion prevention layer, and heat treatment. A step of diffusing the dopant in the applied dopant diffusion solution to the surface layer portion of the semiconductor substrate to form a dopant diffusion layer, and removing the diffusion prevention layer from the semiconductor substrate on which the dopant diffusion layer is formed And a process for producing a semiconductor substrate with a dopant diffusion layer, comprising: a polyvinyl alcohol-based resin (component A) and metal oxide fine particles (component B) as the diffusion-preventing layer forming coating solution. Using a diffusion barrier layer forming coating solution effectively forms a dopant diffusion layer on a semiconductor substrate while preventing diffusion of the dopant to other than the desired location. It can be.

And in the manufacturing method of the solar cell provided with the semiconductor substrate with a dopant diffusion layer, when the semiconductor substrate with a dopant diffusion layer is formed by the above-described manufacturing methods, the solar cell can be efficiently manufactured.

It is explanatory drawing which shows an example of the manufacturing process in the manufacturing method of the semiconductor substrate with a dopant diffusion layer of this invention. It is explanatory drawing which shows the other example of a manufacturing process in the manufacturing method of the semiconductor substrate with a dopant diffusion layer of this invention.

Next, modes for carrying out the present invention will be specifically described, but the present invention is not limited to these.

The coating solution for forming the diffusion preventing layer of the present invention contains a polyvinyl alcohol resin (hereinafter abbreviated as “PVA resin”) (A component) and metal oxide fine particles (B component). Moreover, as the solvent, water is mainly used and alcohol is used together as needed. Thus, since the coating liquid for forming the diffusion preventing layer of the present invention is water-based, it is different from conventional organic solvent-based coating solutions. Hereinafter, each of these materials will be described.

[PVA resin]
The PVA resin used in the coating solution for forming the diffusion prevention layer of the present invention has a saponification degree (measured in accordance with JIS K 6726) of usually 60 to 100 mol%, preferably 70 to 99.9. Those having a mol%, more preferably 80 to 99.9 mol%, particularly preferably 90 to 99.9 mol%, still more preferably 97 to 99.8 mol% are used. That is, if the degree of saponification is too low, the solubility of the PVA-based resin in water decreases, and it may be difficult to obtain a uniform coating solution.

The average polymerization degree (measured in accordance with JIS K 6726) of the PVA resin is usually 100 to 8000, preferably 100 to 4000, more preferably 200 to 2000, and still more preferably 250. Those of ~ 1500 are used. That is, if the average degree of polymerization is too small, the coating solution becomes low in viscosity, so that the coating film becomes a thin film, and the dispersibility of the metal oxide fine particles is insufficient, so that sufficient diffusion preventing performance can be obtained. This is because, on the contrary, when the average degree of polymerization is too large, the coatability tends to be lowered.

The PVA resin used for the coating solution for forming the diffusion preventing layer may be unmodified polyvinyl alcohol or various known modified polyvinyl alcohols. These may be used alone or in combination of two or more.

In particular, when a PVA resin having a 1,2-diol structural unit represented by the following general formula (1) is used as the PVA resin, it is difficult for the coating liquid to thicken over time. Therefore, it is preferable because higher effects such as good coating accuracy and printing accuracy can be obtained over a long period of time.

From the above viewpoint, among the PVA resins having a 1,2-diol structural unit represented by the general formula (1), R ¹ to R ³ and R ⁴ to R ⁶ in the general formula are all hydrogen. A PVA resin having an atom and X being a single bond, that is, a 1,2-diol structural unit represented by the following general formula (1 ′) is preferable.

In the structural unit represented by the general formula (1), R ¹ to R ³ and R ⁴ to R ⁶ may be organic groups as long as they do not significantly impair the resin characteristics. Examples of the organic group include an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. Moreover, the said organic group may have functional groups, such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, and a sulfonic acid group, as needed.

X in the 1,2-diol structural unit represented by the general formula (1) is most preferably a single bond in terms of thermal stability and stability under high temperature and acidic conditions. preferable. However, a binding chain may be used as long as the effect of the present invention is not impaired. Examples of such a linking chain include hydrocarbons such as alkylene, alkenylene, alkynylene, phenylene and naphthylene (these hydrocarbons may be substituted with halogen such as fluorine, chlorine and bromine), -O-, — (CH ₂ O) _m —, — (OCH ₂ ) _m —, — (CH ₂ O) _m CH ₂ —, —CO—, —COCO—, —CO (CH ₂ ) _m CO—, —CO (C ₆ H ₄ ) CO—, —S—, —CS—, —SO—, —SO ₂ —, —NR—, —CONR—, —NRCO—, —CSNR—, —NRCS—, —NRNR—, —HPO _{4 -, - Si (OR)} 2 -, - OSi (OR) 2 -, - OSi (OR) 2 O -, - Ti (OR) 2 -, - OTi (OR) 2 -, - OTi (OR) 2 O-, -Al (OR)-, -OAl (OR)-, -OAl (OR) O-, etc. Any substituents independently a hydrogen atom, an alkyl group preferably, and m is a natural number) and the like.
Among these, an alkylene group having 6 or less carbon atoms, particularly a methylene group, or —CH ₂ OCH ₂ — is preferable from the viewpoint of stability during production or use.

The production method of the PVA resin used in the coating solution for forming the diffusion preventing layer of the present invention is not particularly limited. For example, (i) a co-polymer of a vinyl ester monomer and a compound represented by the following general formula (2) A method of saponifying a polymer, (ii) a method of saponifying and decarboxylating a copolymer of a vinyl ester monomer and a compound represented by the following general formula (3), and (iii) a vinyl ester monomer A method of saponifying and deketalizing a copolymer with a compound represented by the following general formula (4) is preferably used.

In the general formulas (2), (3), and (4), R ¹ to R ⁶ and X are all the same as those in the general formula (1). In the general formula (2), R ⁷ and R ⁸ are each independently a hydrogen atom or R ⁹ —CO— (wherein R ⁹ is an alkyl group having 1 to 4 carbon atoms). In the general formula (4), R ¹⁰ and R ¹¹ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

Among the methods (i) to (iii), in the method (i), the compound represented by the general formula (2) is 3, from the viewpoint of excellent copolymerization reactivity and industrial handleability. 4-diasiloxy-1-butene is preferably used, and 3,4-diacetoxy-1-butene is particularly preferably used.

In addition, when vinyl acetate is used as the vinyl ester monomer used in the method for producing the PVA resin of (i) above, each of the copolymerized copolymer with 3,4-diacetoxy-1-butene is used. The monomer reactivity ratio r is r (vinyl acetate) = 0.710 and r (3,4-diacetoxy-1-butene) = 0.701. This is because when vinyl acetate is copolymerized with the compound of formula (3) (vinyl ethylene carbonate) used in the method for producing the PVA resin (ii), r (vinyl acetate) = Compared with 0.85 and r (vinyl ethylene carbonate) = 5.4, 3,4-diacetoxy-1-butene is excellent in copolymerization reactivity with vinyl acetate.

The chain transfer constant of 3,4-diacetoxy-1-butene is Cx (3,4-diacetoxy-1-butene) = 0.003 (65 ° C.), which is Cx (vinyl ethylene) of vinyl ethylene carbonate. Carbonate) = 0.005 (65 ° C.), and Cx (2,2) -dimethyl-4-vinyl-1,3-dioxolane which is a compound of the general formula (4) used in the method (iii) 2-dimethyl-4-vinyl-1,3-dioxolane) = 0.023 (65 ° C.). This indicates that 3,4-diacetoxy-1-butene is unlikely to cause a decrease in the polymerization rate.

In addition, 3,4-diacetoxy-1-butene is a by-product generated during saponification of the copolymer, and is a by-product generated during the saponification from a structural unit derived from vinyl acetate that is frequently used as a vinyl ester monomer. Is the same as Therefore, it is not necessary to provide a special apparatus or process for the post-treatment or solvent recovery system, and it is an industrially significant advantage that conventional equipment can be used.

3,4-diacetoxy-1-butene can be synthesized, for example, by an epoxy butene derivative described in WO 00/24702, USP 5,623,086, USP 6,072,079, 1,4-diacetoxy-1-butene, which is an intermediate product in the diol production process, can be produced by isomerization using a metal catalyst such as palladium chloride. At the reagent level, Across products can be obtained from the market.

By the way, if the PVA resin obtained by the method (ii) or (iii) is insufficiently decarboxylated or deacetalized, a carbonate ring or an acetal ring remains in the side chain. When such a PVA-based resin is formulated in the coating solution for forming the diffusion preventing layer of the present invention, the dispersibility of the metal oxide fine particles in the coating solution tends to be insufficient. Therefore, also from this point, the PVA resin obtained by the method (i) is preferably used in the present invention.

Examples of the vinyl ester monomers used in the methods (i) to (iii) include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, and vinyl caprate. Vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate, etc., and vinyl acetate is preferably used economically.

In addition to the above-described monomers (vinyl ester monomers, compounds represented by the general formulas (2), (3), and (4)), a range that does not significantly affect the physical properties of the resin, for example, 20 mol% or less If so, other copolymer components may be contained. Examples of the copolymer component include α-olefins such as ethylene and propylene; hydroxy group-containing α such as 3-buten-1-ol, 4-penten-1-ol, and 5-hexene-1,2-diol. -Derivatives such as olefins and acylated products and esterified products thereof; unsaturated acids such as itaconic acid, maleic acid and acrylic acid, or salts or mono- or dialkyl esters thereof; nitriles such as acrylonitrile, methacrylamide, diacetone acrylamide, etc. Amides, ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, olefin sulfonic acid such as AMPS (acrylamido-2-methylpropane sulfonic acid) or a salt thereof, and the like.

The content of 1,2-diol structural units contained in the PVA resin in the coating solution for forming the diffusion preventing layer of the present invention is preferably 0.5 to 30 mol%, more preferably 1 to 20 It is in the range of mol%, more preferably 3 to 15 mol%. That is, if the content is too low, the effect of using a PVA resin into which a 1,2-diol structural unit is introduced tends to be too low. On the other hand, if the content is too high, the drying property is lowered and the productivity is lowered. Because there is a tendency to.

The content of the 1,2-diol structural unit in the PVA resin was determined by ¹ H-NMR spectrum (solvent: DMSO-d6, internal standard substance: tetramethylsilane) of a completely saponified PVA resin. Specifically, from the peak area derived from the hydroxyl proton, methine proton, and methylene proton in the 1,2-diol unit, methylene proton in the main chain, hydroxyl proton linked to the main chain, etc. What is necessary is just to calculate.

The content of the PVA resin in the coating solution for forming the diffusion preventing layer of the present invention is usually 1 to 40% by weight, preferably 5 to 30% by weight, more preferably 10 to 25% by weight. That is, if the content of the PVA-based resin is too small, the viscosity of the coating liquid tends to be low, and the coating film tends to be difficult to be formed stably. Conversely, if the content is too large, the viscosity of the coating liquid increases. For this reason, the coating workability is likely to be lowered, and further, when screen printing is performed, the screen mesh tends to be clogged.

[Metal oxide fine particles]
In the coating liquid for forming the diffusion preventing layer of the present invention, metal oxide fine particles are blended together with the PVA resin. The metal oxide species of the fine particles is at least one selected from Group 4 metal oxides, Group 5 metal oxides, and Group 13 metal oxides of the Periodic Table. Specifically, periodic table group 4 metal oxides such as titanium oxide and zirconium oxide, periodic table group 5 metal oxides such as vanadium oxide, niobium oxide, and tantalum oxide, and periodic periods such as aluminum oxide and gallium oxide. Table 13 Group 13 metal oxides. These may be used alone or in combination of two or more. Among these, from the viewpoint of diffusion prevention and affinity with a dopant, metal oxides of Group 4 and Group 13 of the periodic table are preferable, and aluminum oxide and titanium oxide are particularly preferable. In addition, metal oxide fine particles that are amphoteric oxides are preferred, and fine particles made of aluminum oxide are more preferred.

From the viewpoint of preventing diffusion, the metal oxide fine particles have an average primary particle size of usually 1 to 500 nm, preferably 3 to 200 nm, particularly preferably 3 to 50 nm, and particularly preferably 3 to 20 nm. The average primary particle size is a value calculated from the BET specific surface area of the metal oxide fine particles.

In the present invention, a plurality of metal oxide fine particles having different average primary particle sizes can be used. At that time, the average primary particle size is relatively small (for example, the average primary particle size is 1 to 50 nm, preferably 1 to 20 nm), and the average primary particle size is relatively large (for example, the average primary particle size is more than 50 to 500 nm, preferably Are used at the same time, it is possible to reduce the gaps between the metal oxide fine particles in the coating film after coating the coating solution, thereby improving the uniformity of the coated surface.

The content of the metal oxide fine particles in the coating solution for forming the diffusion preventing layer of the present invention is usually 0 in terms of the total amount of metal oxide fine particles, even when a plurality of fine particles having different average primary particle sizes are contained. 0.1 to 40% by weight, preferably 0.5 to 35% by weight, more preferably 0.8 to 30% by weight, still more preferably 5 to 30% by weight, and particularly preferably 10 to 30% by weight. is there. The content of the metal oxide fine particles with respect to 100 parts by weight of the PVA resin is usually 0.05 to 200 parts by weight, preferably 10 to 180 parts by weight, more preferably 30 to 150 parts by weight, particularly preferably. Is in the range of 50 to 120 parts by weight. That is, if the content of the metal oxide fine particles is too small, the desired anti-diffusion performance cannot be obtained. Conversely, if the content of the metal oxide fine particles is too large, the coating property and the like are hindered. This is because it comes to come.

〔water〕
In the coating solution for forming the diffusion preventing layer of the present invention, as described above, water is used as the solvent. As water used for the said coating liquid for diffusion prevention layer formation, what has few impurities, such as an alkali metal and a heavy metal, and a foreign material is preferable, Usually, total organic carbon (henceforth TOC) may be 50 ppb or less, Preferably, it is 10 ppb or less, and the electrical resistivity is usually 16 MΩ · cm or more, preferably 17 MΩ · cm or more, more preferably 18 MΩ · cm or more. Ultrapure water is most preferable, but ion-exchanged water or distilled water can also be used.

The water content in the coating solution for forming the diffusion preventing layer of the present invention is usually 10 to 80% by weight, preferably 15 to 75% by weight, more preferably 20 to 70% by weight, and particularly preferably 20 to 50% by weight. % Range. That is, if the water content is too small, the viscosity of the coating solution becomes too high, the coating workability tends to be lowered, and further, when screen printing is performed, the screen mesh tends to be clogged. This is because, if the amount is too large, the viscosity becomes too low to form a coating film stably.

Conventional organic solvent-based anti-diffusion layer forming solutions have a problem in that printing tends to become unstable when continuous printing is performed by screen printing or the like because the solvent easily volatilizes. However, in the present invention, by using a PVA resin (component A), it is possible to obtain a coating solution for forming a diffusion preventing layer containing usually 10 to 80% by weight of water. Such a water-based anti-diffusion layer forming coating solution is less volatile than an organic solvent-based anti-diffusion layer forming solution, and is excellent in film-forming properties by screen printing or the like.

[Other materials]
As described above, the diffusion-preventing layer forming coating liquid of the present invention contains a PVA-based resin, metal oxide fine particles, and water as a solvent. However, if necessary, other materials such as known general alcohols, surfactants, inorganic fine particles and the like can be further blended.

When an alcohol is added to the coating solution for forming the diffusion preventing layer, the storage stability and flow stability of the coating solution and the leveling property of the coating film can be improved. Specific examples of the alcohols include monohydric alcohols such as methanol (65 ° C.), ethanol (78 ° C.), and isopropanol (82 ° C.); ethylene glycol (197 ° C.), diethylene glycol (244 ° C.), triethylene Dihydric alcohols such as glycol (287 ° C.), tetraethylene glycol (314 ° C.), propylene glycol (188 ° C.); glycerin (290 ° C.), trimethylolpropane (292 ° C.), sorbitol (296 ° C.), mannitol (290) ˜295 ° C.), pentaerythritol (276 ° C.), trihydric or higher polyhydric alcohols such as polyglycerin; and ethylene glycol monomethyl ether (124 ° C.), ethylene glycol monoethyl ether (136 ° C.), ethylene glycol mono- n- Chirueteru (171 ° C.), propylene glycol monomethyl ether (120 ° C.), can be mentioned alcohol derivatives such as diethylene glycol monomethyl ether (methyl carbitol) (194 ° C.). In addition, the temperature in said () shows a boiling point. These alcohols may be used independently and may use 2 or more types together.

In particular, it is preferable to use alcohols having a boiling point higher than that of water, that is, alcohols having a boiling point of 100 to 350 ° C., in that rapid drying of the coated film after printing is suppressed and the leveling property is greatly improved. More preferably, the boiling point is 150 to 350 ° C., and still more preferably, the boiling point is 190 to 300 ° C. This is because when the boiling point is too high, there is a tendency to require drying at a high temperature for a long time when alcohols are used.

When an alcohol is blended in the coating solution for forming the diffusion preventing layer of the present invention, the blending amount is usually 5 to 70 parts by weight, preferably 10 to 60 parts by weight, more preferably based on the total amount of the coating solution. Is in the range of 30 to 50 parts by weight. The blending amount of the alcohol with respect to 100 parts by weight of water is usually 5 to 200 parts by weight, preferably 20 to 170 parts by weight, more preferably 80 to 150 parts by weight. That is, if the content of such alcohols is too small, the fluidity improving effect and the leveling effect cannot be obtained sufficiently. On the other hand, if the content is too large, the solubility of the PVA resin is lowered and a uniform coating solution is obtained. This is because it tends to be difficult to be made.

In addition, when a surfactant is added to the coating solution for forming the diffusion preventing layer of the present invention, wettability to the semiconductor surface is improved, foaming of the coating solution is further suppressed, and printing defects caused by bubbles are prevented. Is preferable. Surfactants used in the coating solution can be broadly classified into nonionic surfactants, cationic surfactants, and anionic surfactants, and any of them can be used. Of these, nonionic surfactants are preferred because they are less likely to bring metal components into the semiconductor.

Examples of the nonionic surfactant include hydrocarbon surfactants such as ethylene oxide-propylene oxide block copolymers and acetylene glycol derivatives, silicon surfactants, and fluorine surfactants. Of these, hydrocarbon surfactants, particularly acetylene glycol derivatives, are preferably used in the coating solution for forming the diffusion preventing layer because they are excellent in suppressing foaming and defoaming.

As the acetylene glycol derivative, those represented by the following general formula (5) are preferably used.

R ¹² and R ¹⁵ in the general formula (5) each independently represents an alkyl group having 1 to 20 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms, more preferably 3 to 5 carbon atoms. It is an alkyl group. R ¹³ and R ¹⁴ each independently represents an alkyl group having 1 to 3 carbon atoms, and a methyl group is particularly preferred. R ¹² and R ¹⁵ , and R ¹³ and R ¹⁴ may be the same or different, but those having the same structure are preferably used. In the general formula (5), n and m are integers from 0 to 30, respectively.
In particular, m + n is preferably 1 to 10, more preferably m + n is 1 to 5, and still more preferably m + n is 1 to 3.

Specific examples of the acetylene glycol derivative include 2,5,8,11-tetramethyl-6-dodecin-5,8-diol ethylene oxide adduct, 5,8-dimethyl-6-dodecin-5, 8-diol ethylene oxide adduct, 2,4,7,9-tetramethyl-5-decyne-4,7diol ethylene oxide adduct, 4,7-dimethyl-5-decyne-4,7-diol Ethylene oxide adduct, 2,3,6,7-tetramethyl-4-octyne-3,6diol ethylene oxide adduct, 3,6-dimethyl-4-octyne-3,6-diol ethylene oxide adduct 2,5-dimethyl-3-hexyne-2,5-diol ethylene oxide adduct and the like.
Among these, an ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7 diol having an ethylene oxide addition amount (m + n) of 1 to 2, Preferably used.

Examples of such commercially available acetylene glycol derivatives (surfactants) include the Surfinol series manufactured by Nissin Chemical Industry.

When a surfactant is added to the coating solution for forming the diffusion preventing layer of the present invention, the amount is usually 0.01 to 10% by weight, preferably 0.1 to 8%, based on the total amount of the coating solution. % By weight, more preferably in the range of 0.3 to 5% by weight. That is, if the amount of such a surfactant is too small, the anti-foaming / defoaming effect tends to be low, and conversely if too large, it tends to be difficult to obtain a uniform solution by separating from the liquid. Because.

In addition, in the coating solution for forming the diffusion preventing layer of the present invention, various inorganic fine particles other than the metal oxide fine particles can be blended for the purpose of improving screen printing characteristics and the like.

As the inorganic fine particles, silicas such as colloidal silica, amorphous silica, and fumed silica are preferable, and colloidal silica is more preferably used.

The blending amount of such inorganic fine particles is usually 0.5 to 20% by weight, preferably 1 to 10% by weight in the coating solution.

(Preparation of coating solution for forming diffusion preventing layer)
As described above, the diffusion-preventing layer-forming coating solution of the present invention contains a PVA-based resin, metal oxide fine particles, and water as a solvent. Other materials such as an activator and inorganic fine particles are further blended. And as a preparation method of the said coating liquid, after making PVA resin into aqueous solution, for example, the method of mix | blending metal oxide microparticles | fine-particles and another additive in this, and other additives are previously aqueous solution in the said method In addition, a method in which a PVA resin and metal oxide fine particles are mixed, put into water, heated and dissolved while stirring, and then other additives are added.

In the method of applying the coating solution for forming the diffusion preventing layer prepared as described above to a part of the surface of the semiconductor substrate and forming the diffusion preventing layer on the surface of the semiconductor substrate, the coating property resulting from the uniformity of the solution Printing stability can be obtained. In other words, conventional organic solvent-based anti-diffusion layer-forming solutions have insufficient dispersibility of metal oxide fine particles, and thus there is a problem that it is difficult to form a uniform-thickness coating film particularly by spin coating. In addition, since the solvent easily volatilizes, when continuous printing is performed by screen printing or the like, there has been a problem that printing tends to become unstable. However, in the present invention, these can be solved by the above method.

[Production method of semiconductor substrate with dopant diffusion layer]
Examples of a method for obtaining a semiconductor substrate with a dopant diffusion layer by forming a dopant diffusion layer on the surface of the semiconductor substrate using the coating solution for forming the diffusion prevention layer include the following methods (I) and (II): can give.

(I) A step of forming a diffusion preventing layer by applying a coating solution for forming a diffusion preventing layer on a part of the surface of the semiconductor substrate, and a diffusion of the dopant on the surface of the semiconductor substrate with the diffusion preventing layer, thereby preventing the diffusion. A semiconductor substrate with a dopant diffusion layer is manufactured by a step of making a surface layer portion of a semiconductor substrate on which no layer is formed a dopant diffusion layer and a step of removing the diffusion prevention layer from the semiconductor substrate on which the dopant diffusion layer is formed. Method.

(II) After applying the dopant diffusion solution to a part of the semiconductor substrate surface, coating the diffusion prevention layer forming coating solution so as to cover the coating surface, and forming a diffusion prevention layer, and heat treatment And a step of diffusing the dopant in the applied dopant diffusion solution to the surface layer portion of the semiconductor substrate to form a dopant diffusion layer, and a diffusion prevention layer from the semiconductor substrate on which the dopant diffusion layer is formed. The method of manufacturing a semiconductor substrate with a dopant diffusion layer by the process to remove.

FIG. 1 specifically shows the manufacturing process shown in (I), which is performed in the order of (i) to (iv). Referring to FIG. 1 in detail, (i) shows a state in which a diffusion prevention layer forming coating solution is applied to one surface of a semiconductor substrate 1 to form a diffusion prevention layer 3, and (ii) shows the atmosphere of a dopant gas ( For example, a state in which a dopant gas is brought into contact with the surface of the semiconductor substrate 1 with the diffusion prevention layer 3 filled with phosphorus oxychloride (POCl ₃ ) gas or boron tribromide (BBr ₃ ) gas) is shown. ) Shows a state in which the dopant (for example, phosphorus or boron) is diffused into the surface of the semiconductor substrate 1 on the surface where the diffusion prevention layer 3 is not formed by contacting the gas to form the dopant diffusion layer 11. That is, the diffusion of the dopant is prevented on the surface of the semiconductor substrate 1 on which the diffusion preventing layer 3 is formed. And (iv) has shown the state which removed the diffusion prevention layer 3 from the semiconductor substrate 1 in which the dopant diffusion layer 11 was formed.

FIG. 2 specifically shows the manufacturing process shown in (II), which is performed in the order of (i) to (iv) shown in the figure. Referring to FIG. 2 in detail, (i) shows a state in which a dopant diffusion solution is applied to one surface of the semiconductor substrate 1 to form dopant solution application layers 2a and 2b, and (ii) shows the application of the dopant solution. The diffusion preventing layer forming coating solution is applied so as to cover the

layers

2a and 2b, and the diffusion preventing layer 3 is formed. (Iii) is a heat treatment, and the dopant solution coating layer 2a, The dopant in 2b is diffused in the surface layer portion of the semiconductor substrate 1 to form the

dopant diffusion layers

11a and 11b. That is, some dopants vaporized from the dopant solution coating layers 2a and 2b by the heat treatment cause an out-diffusion phenomenon (a phenomenon in which the dopant is diffused outside the formation surface of the dopant solution coating layers 2a and 2b of the semiconductor substrate 1) The diffusion preventing layer 3 prevents the dopant in the

dopant diffusion layers

11a and 11b from being used only for forming the

dopant diffusion layers

11a and 11b. (Iv) shows a state in which the diffusion preventing layer 3 is removed from the semiconductor substrate 1 on which the

dopant diffusion layers

11a and 11b are formed.

The heat treatment in the production process shown in (II) above means the following drying process, firing process, and diffusion process.

In the drying process, volatile components such as water are removed from the coating layer. The conditions may be set as appropriate, but are usually 1 to 60 minutes, particularly 5 to 30 minutes under a temperature condition of 20 to 300 ° C., particularly 100 to 200 ° C. The drying method is not particularly limited, and the drying is performed by a known method such as hot air drying, infrared heat drying, or vacuum drying.

In the subsequent firing step, most of the volatile components in the coating layer are removed using an electric furnace or the like. The conditions of such a process need to be adjusted as appropriate depending on the composition of the solution and the thickness of the coating layer, but are usually 300 to 1000 ° C., particularly 400 to 800 ° C., 1 to 120 minutes, particularly 5 to 60 minutes Will be implemented in the time.

After the firing step, the dopant is further diffused in the semiconductor substrate in the diffusion step, and a diffusion layer is formed. In the diffusion step, an electric furnace or the like is used in the same manner as in the firing step, and is performed under a temperature condition of 800 to 1400 ° C., in a state of single wafers or a plurality of stacked sheets.

It should be noted that these steps can be carried out as a heat treatment continuously as one step, and in some cases, some steps can be omitted.

Examples of the semiconductor substrate 1 used in the manufacturing method shown in the above (I) and (II) include those made of single crystal or polycrystalline p-type silicon, those made of single crystal or polycrystalline n-type silicon, gallium A material made of doped p-type or n-type silicon is used. In the case of a single crystal, the semiconductor substrate 1 may be manufactured by any one of the Czochralski (CZ) method and the float zone (FZ) method. Furthermore, when the semiconductor substrate 1 is used as a material for a solar cell, a minute uneven shape is formed on the surface (light-receiving surface) of the semiconductor substrate 1 by etching or the like in order to reduce the reflectance in the visible light region. It is preferable.

And in the method shown in said (I) and (II), when the spreading | diffusion prevention layer forming coating liquid of this invention is used, a dopant is effectively made into a semiconductor substrate, preventing the spreading | diffusion of a dopant to other than a desired location. A diffusion layer can be formed.

In addition, in the methods shown in (I) and (II) above, various coating methods such as spin coating, spraying, offset printing, and screen printing can be used as the coating method of the coating solution for forming the diffusion preventing layer of the present invention. Applied. Among these, screen printing is preferable because it is easy to form a uniform coating film in a wide range, and since the coating solution is water-based, there is an advantage that printing is not easily destabilized even if continuous printing is performed. .

By the way, in the method shown in (I) above, the dopant may be diffused by a method of applying a dopant diffusion solution in addition to a method of diffusing the dopant by gas contact. For example, an aqueous solution of phosphoric acid or boric acid is used for this solution.

Also, water-soluble compounds such as phosphoric acids and boric acids are used for the dopant diffusion solution used in the method shown in (II) above. The dopant diffusing solution may be blended with materials such as PVA resins, alcohols, surfactants, inorganic fine particles, and the like from the viewpoints of coating properties, forming properties of the dopant solution coating layer, and the like. In addition, as a coating method of the said dopant diffusion solution, various coating methods, such as a spin coat method, offset printing, and screen printing, are normally applied.

In the methods shown in (I) and (II) above, as a method for removing the diffusion prevention layer from the semiconductor substrate on which the dopant diffusion layer is formed, for example, an immersion treatment in hydrofluoric acid (HF) is performed. preferable. In such immersion treatment, hydrofluoric acid is usually used as an aqueous solution of 3 to 50% by weight, and for the purpose of improving the treatment efficiency, the immersion treatment is heated or irradiated with ultrasonic waves. This is also a preferred embodiment. The dopant glass (phosphorus glass, boron glass, etc.) formed on the surface of the dopant diffusion layer is also removed by the immersion treatment in hydrofluoric acid.

Further, after the immersion treatment in hydrofluoric acid (HF), the immersion treatment in a basic liquid may be performed. By such treatment, it is possible to remove metal oxide residues. Examples of the basic liquid include a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution. The concentration of the basic liquid is usually 0.1 to 10% by weight in terms of workability, and preferably 0.02 to 5% by weight, particularly preferably in terms of preventing excessive etching of the substrate surface. 0.2 to 1% by weight. Furthermore, the working temperature is preferably 50 ° C. or less, more preferably room temperature, specifically 20 to 30 ° C. in terms of preventing excessive etching of the substrate surface. In addition, the immersion time in the basic liquid is preferably 5 minutes or less, more preferably 1 minute or less in terms of preventing excessive etching of the substrate surface.

In addition, in the manufacturing method of the solar cell provided with the semiconductor substrate with the dopant diffusion layer, when the semiconductor substrate with the dopant diffusion layer is formed by the method as shown in the above (I) and (II), the solar cell is efficiently produced. Can be manufactured.

And since the semiconductor substrate with a dopant diffused layer manufactured by the method as shown to said (I) and (II) has a favorable pn junction structure, generation | occurrence | production of a leakage current can be suppressed. Therefore, incorporating the semiconductor substrate with a dopant diffusion layer manufactured by the above method into various semiconductor devices including solar cells can contribute to improving the quality of the semiconductor device. Note that examples of the semiconductor device include a solar cell, a diode, and a transistor.

Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded. In the examples, “parts” and “%” mean weight basis unless otherwise specified.
In the examples, ultrapure water means water having a TOC of 1.0 ppb or less and an electrical resistivity of 18.2 MΩ · cm.

First, prior to Examples and Comparative Examples, unmodified PVA (a) (saponification degree 78 mol%, average polymerization degree 1400) and modified PVA (a) (saponification degree 98.9 mol%, average polymerization degree 350). 1, 2-diol structure-containing PVA) having a modification degree of 8 mol%. The modified PVA (a) was produced as follows.

<Production of modified PVA (a)>
A reaction vessel equipped with a reflux condenser, a dropping funnel and a stirrer was charged with 1500 parts of vinyl acetate, 800 parts of methanol, and 240 parts of 3,4-diacetoxy-1-butene, and 0.05 mol% of asobisisobutyronitrile. (Various charged vinyl acetate) was charged, the temperature was raised under a room air flow while stirring, and polymerization was started while refluxing. When the polymerization rate of vinyl acetate reached 87%, m-dinitrobenzene was added to complete the polymerization, and then unreacted vinyl acetate monomer was removed out of the system by blowing methanol vapor. A combined methanol solution was obtained.

Next, the methanol solution was further diluted with methanol, adjusted to a concentration of 40%, charged into a kneader, and a 2% methanol solution of sodium hydroxide was added to the vinyl acetate structural unit in the copolymer while maintaining the solution temperature at 40 ° C. Further, saponification was carried out by adding 8 mmol with respect to 1 mol of the total amount of 3,4-diacetoxy-1-butene structural units. As saponification progressed, when saponified substances were precipitated and became particulate, they were separated by filtration, washed well with methanol and dried in a hot air dryer to obtain the desired modified PVA (a).

The degree of saponification of the obtained modified PVA (a) was 98.9 mol% when analyzed by the alkali consumption required for hydrolysis of residual vinyl acetate and 3,4-diacetoxy-1-butene. The average degree of polymerization was 350 when analyzed according to JIS K 6726. The content of the 1,2-diol structural unit represented by the general formula (1) is ¹ H-NMR (300 MHz proton NMR, DMSO-d6 solution, internal standard substance: tetramethylsilane, 50 ° C.). It was 8 mol% when it computed from the integrated value measured in this way.

[Example 1]
<Preparation of coating solution (α) for forming diffusion preventing layer>
22 parts of modified PVA (a) was added to 36.5 parts of ultrapure water, and dissolved while stirring under heating to prepare a solution (α1). Further, 40 parts of glycerin, ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol as a surfactant (Shinfin Chemical 420, Surfynol 420) 5 parts were added to prepare a solution (α2). In this solution (α1), 1.0 part of aluminum oxide fine particles (manufactured by Daimei Chemical Industry Co., Ltd., Tymicron TM-300, BET specific surface area 220 m ² / g, average primary particle size 7 nm (calculated from BET specific surface area value)) Then, the solution (α2) was further added and stirred to prepare an aqueous diffusion barrier layer forming coating solution (α).

<Application to semiconductor substrate>
Screen-printing was performed on one side of a semiconductor substrate (p-type single crystal silicon, with alkali etching texture, 156 mm square, 200 μm thickness) using the coating liquid for forming the diffusion prevention layer (α) prepared above under the following printing conditions. Then, a diffusion preventing layer was formed (see FIG. 1 (i)).
(Printing conditions)
Printing machine: “LS-34GX” manufactured by Neurong Seimitsu Kogyo Co., Ltd.
Squeegee: NM squeegee (Hardness: 60) manufactured by Neurong Precision Industry Co., Ltd.
Squeegee angle: 80 degrees Scraper: NM squeegee (Hardness: 60) made by Neurong Seimitsu Kogyo
Scraper angle: 86 degrees Printing pressure; 0.2 MPa
Screen version: manufactured by Tokyo Process Service Co., Ltd. Plate size: 450 mm square Mesh type: V330
Application thickness: 2 μm (after drying)
Pattern: Wafer whole surface printing Printing environment: 23 ° C, 60% RH
Drying conditions: 150 ° C, 2 minutes

<Diffusion>
Next, 10 semiconductor substrates on which the diffusion preventing layer is formed are arranged at intervals of 5 mm on a jig in a horizontal tube electric furnace containing POCl ₃ (phosphorus oxychloride) at 840 ° C. Phosphorus diffusion (thermal diffusion) was performed for a minute. Thereafter, the PSG (phosphorus glass) layer and the diffusion prevention layer were removed by immersing in a 46 wt% hydrofluoric acid (HF) aqueous solution (prepared with ultra pure water) for 3 minutes, and then with ultra pure water. Washing and drying at 150 ° C. (10 minutes) were performed (see FIGS. 1 (ii) to (iv)).

<Measurement of surface resistance value>
Using a resistance measuring instrument (manufactured by Mitsubishi Chemical Analytech Co., Ltd., Lorester (using a PSP probe)), the surface resistance value was measured by placing the four probes on arbitrary positions on the surface of the semiconductor substrate after the diffusion treatment.

<Measurement results>
The surface resistance of the surface of the semiconductor substrate after the diffusion treatment on which the coating solution for forming the diffusion preventing layer was not applied was 60 Ω / □, whereas the surface resistance of the surface on which the coating solution for forming the diffusion preventing layer was applied. Was 1000Ω / □ or more. Therefore, it can be seen that the diffusion preventing property by the diffusion preventing layer completely prevents the diffusion of phosphorus to the diffusion preventing layer forming surface of the semiconductor substrate.

[Example 2]
Same as Example 1, except that 31.5 parts of ultrapure water was used in the coating solution (α) for forming the diffusion preventing layer used in Example 1, ethylene glycol was used instead of glycerin, and 6.0 parts of aluminum oxide fine particles were used. Thus, a water-based anti-diffusion layer forming coating solution was prepared. Then, “application to semiconductor substrate”, “diffusion”, and “measurement of surface resistance value” were performed in the same manner as in Example 1 except that this coating solution for forming the diffusion prevention layer was used.

Example 3
In the coating liquid (α) for forming the diffusion preventing layer used in Example 1, the above-mentioned unmodified PVA (a) (saponification degree 78 mol%, average polymerization degree 1400) was used instead of the modified PVA (a). Then, a coating solution for forming a diffusion preventing layer was prepared. Then, “application to semiconductor substrate”, “diffusion”, and “measurement of surface resistance value” were performed in the same manner as in Example 1 except that this coating solution for forming the diffusion prevention layer was used.

As a result, the surface resistance of the surface of the semiconductor substrate after the diffusion treatment on which the coating solution for forming the diffusion preventing layer was not applied was 60Ω / □, whereas the surface resistance of the surface on which the coating solution for forming the diffusion preventing layer was applied. The surface resistance was 1000Ω / □. Therefore, it can be seen that the diffusion preventing property by the diffusion preventing layer completely prevents the diffusion of phosphorus to the diffusion preventing layer forming surface of the semiconductor substrate.

Example 4
In the coating liquid (α) for forming the diffusion preventing layer used in Example 1, the above-mentioned unmodified PVA (a) (saponification degree 78 mol%, average polymerization degree 1400) was used instead of the modified PVA (a). A water-based anti-diffusion layer forming coating solution was prepared in the same manner except that 31.5 parts of ultrapure water was used, ethylene glycol was used instead of glycerin, and 6.0 parts of aluminum oxide fine particles were used. Then, “application to semiconductor substrate”, “diffusion”, and “measurement of surface resistance value” were performed in the same manner as in Example 1 except that this coating solution for forming the diffusion prevention layer was used.

<Measurement results>
The surface resistance of the surface of the semiconductor substrate after the diffusion treatment on which the coating solution for forming the diffusion preventing layer was not applied was 60 Ω / □, whereas the surface resistance of the surface on which the coating solution for forming the diffusion preventing layer was applied. Was 1000Ω / □. Therefore, it can be seen that the diffusion preventing property by the diffusion preventing layer completely prevents the diffusion of phosphorus to the diffusion preventing layer forming surface of the semiconductor substrate.

Example 5
Using the coating liquid for forming the diffusion prevention layer used in Example 2, “application to a semiconductor substrate” and “diffusion” were performed in the same manner as in Example 1.
Thereafter, the obtained semiconductor substrate was immersed in a 46 wt% hydrofluoric acid (HF) aqueous solution for 3 minutes, washed with ultrapure water, and sufficiently dried. Subsequently, as a post-treatment, the semiconductor substrate was immersed in an aqueous NaOH solution (3 wt% (produced with ultrapure water)) for 30 seconds. In this way, after removing the PSG (phosphorus glass) layer and the diffusion prevention layer, washing with ultrapure water and drying at 150 ° C. (10 minutes) were performed (see FIGS. 1 (ii) to (iv)).

As a result of performing “measurement of the surface resistance value” in the same manner as in Example 1, the surface resistance of the surface of the semiconductor substrate after the diffusion treatment on which the coating solution for forming the diffusion preventing layer was not applied was 60Ω / □. In contrast, the surface resistance of the surface coated with the diffusion-preventing layer forming coating solution was 1000 Ω / □ or more. Therefore, it can be seen that the diffusion preventing property by the diffusion preventing layer completely prevents the diffusion of phosphorus to the diffusion preventing layer forming surface of the semiconductor substrate. In addition, the aluminum oxide residue after washing was thin and could be washed cleanly.

Example 6
Using the coating solution for forming a diffusion preventing layer used in Example 4, “application to a semiconductor substrate” and “diffusion” were performed in the same manner as in Example 1.
Thereafter, the obtained semiconductor substrate was immersed in a 46 wt% hydrofluoric acid (HF) aqueous solution for 3 minutes, washed with ultrapure water, and sufficiently dried. Subsequently, as a post-treatment, the semiconductor substrate was immersed in an aqueous NaOH solution (3 wt% (produced with ultrapure water)) for 30 seconds. In this way, after removing the PSG (phosphorus glass) layer and the diffusion prevention layer, washing with ultrapure water and drying at 150 ° C. (10 minutes) were performed (see FIGS. 1 (ii) to (iv)).

As a result of performing “measurement of the surface resistance value” in the same manner as in Example 1, the surface resistance of the surface of the semiconductor substrate after the diffusion treatment on which the coating solution for forming the diffusion preventing layer was not applied was 60Ω / □. In contrast, the surface resistance of the surface coated with the diffusion-preventing layer forming coating solution was 1000Ω / □. Therefore, it can be seen that the diffusion preventing property by the diffusion preventing layer completely prevents the diffusion of phosphorus to the diffusion preventing layer forming surface of the semiconductor substrate. In addition, the aluminum oxide residue after washing was thin and could be washed cleanly.

Example 7
In Example 5, post-treatment with an aqueous NaOH solution was performed in place of an aqueous KOH solution (3 wt% (prepared with ultrapure water)). Otherwise, “application to semiconductor substrate”, “diffusion”, and “cleaning treatment” were performed in the same manner as in Example 5.

Example 8
In Example 6, post-treatment with an aqueous NaOH solution was performed in place of an aqueous KOH solution (3 wt% (prepared with ultrapure water)). Other than that, “application to semiconductor substrate”, “diffusion”, and “cleaning treatment” were performed in the same manner as in Example 6.

Example 9
In Example 7, titanium oxide (manufactured by Nippon Aerosil Co., Ltd., AEROXIDE TiO ₂ P-25, average primary particle size 30 nm) was used in place of aluminum oxide in the coating solution for forming the diffusion prevention layer. Other than that, “application to semiconductor substrate”, “diffusion”, and “cleaning treatment” were performed in the same manner as in Example 7.

As a result of performing “measurement of the surface resistance value” in the same manner as in Example 1, the surface resistance of the surface of the semiconductor substrate after the diffusion treatment on which the coating solution for forming the diffusion preventing layer was not applied was 60Ω / □. In contrast, the surface resistance of the surface coated with the diffusion-preventing layer forming coating solution was 1000 Ω / □ or more. Therefore, it can be seen that the diffusion preventing property by the diffusion preventing layer completely prevents the diffusion of phosphorus to the diffusion preventing layer forming surface of the semiconductor substrate. In addition, the titanium oxide residue after washing was thin and could be washed cleanly.

Example 10
18 parts of modified PVA (a) was added to 29.5 parts of ultrapure water and dissolved while stirring under heating to prepare a solution (ε1). In addition, 0.5 part of ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (Shinfin Chemical Co., Surfynol 420) is added to 40 parts of ethylene glycol. The solution (ε2) was prepared by addition. In this solution (ε1), 12.0 parts of aluminum oxide fine particles (manufactured by Daimei Chemical Industry Co., Ltd., Tymicron TM-300, BET specific surface area 220 m ² / g, average primary particle size 7 nm (calculated from BET specific surface area value)) Then, a solution (ε2) was further added and stirred to prepare an aqueous diffusion barrier layer forming coating solution (ε). And "application | coating to a semiconductor substrate" and "diffusion" were performed like Example 1 except having used this coating liquid (epsilon) for diffusion prevention layer formation.
Thereafter, the obtained semiconductor substrate was immersed in a 46 wt% hydrofluoric acid (HF) aqueous solution for 3 minutes, washed with ultrapure water, and sufficiently dried. Subsequently, as a post-treatment, the semiconductor substrate was immersed in a KOH aqueous solution (3 wt% (produced with ultrapure water)) for 30 seconds. In this way, after removing the PSG (phosphorus glass) layer and the diffusion prevention layer, washing with ultrapure water and drying at 150 ° C. (10 minutes) were performed (see FIGS. 1 (ii) to (iv)).

Then, as a result of performing “measurement of surface resistance value” in the same manner as in Example 1, the surface resistance of the surface of the semiconductor substrate after the diffusion treatment on which the coating solution for forming the diffusion preventing layer was not applied was 60Ω / □. On the other hand, the surface resistance of the surface coated with the coating solution for forming the diffusion preventing layer was 1000Ω / □ or more. Therefore, it can be seen that the diffusion preventing property by the diffusion preventing layer completely prevents the diffusion of phosphorus to the diffusion preventing layer forming surface of the semiconductor substrate. In addition, the aluminum oxide residue after washing was thin and could be washed cleanly.

Example 11
In the coating solution (ε) for forming the diffusion preventing layer used in Example 10, the amount of ultrapure water was 28.5 parts, the amount of ethylene glycol was 35 parts, and Tymicron TM-300 as aluminum oxide fine particles. And 12.0 parts of Tymicron TM-DA (manufactured by Daimei Chemical Industries, BET specific surface area 13.5 m ² / g, average primary particle size 100 nm). Other than that was carried out similarly to Example 10, and performed "application | coating to a semiconductor substrate", "diffusion", and "cleaning process."

Example 12
In the coating solution for forming an anti-diffusion layer used in Example 11, the amount of Tymicron TM-300 was 12.0 parts, and the amount of Tymicron TM-DA was 6.0 parts. Other than that was carried out similarly to Example 11, and performed "application | coating to a semiconductor substrate", "diffusion", and "cleaning process."

Example 13
Using the coating liquid for forming the diffusion preventing layer used in Example 10, screen printing was performed on one side of a semiconductor substrate (p-type single crystal silicon, with alkali etching texture, 156 mm square, 200 μm thickness) under the following printing conditions. Then, a diffusion preventing layer was formed. Otherwise, “diffusion” and “measurement of surface resistance” were performed in the same manner as in Example 1.
(Printing conditions)
Printing machine: “LS-34GX” manufactured by Neurong Seimitsu Kogyo Co., Ltd.
Squeegee: NM squeegee (Hardness: 60) manufactured by Neurong Precision Industry Co., Ltd.
Squeegee angle: 80 degrees Scraper: NM squeegee (Hardness: 60) made by Neurong Seimitsu Kogyo
Scraper angle: 86 degrees Printing pressure; 0.2 MPa
Screen version: manufactured by Tokyo Process Service Co., Ltd. Plate size: 450 mm square Mesh type: V330
Application thickness: 2 μm (after drying)
Pattern: Wafer whole surface printing Printing environment: 23 ° C, 60% RH
Drying conditions: 150 ° C., 10 minutes

<Measurement results>
The surface resistance of the semiconductor substrate after the diffusion treatment on which the coating solution for forming the diffusion preventing layer was not applied was 60Ω / □, whereas the surface resistance of the surface coated with the coating solution for forming the diffusion preventing layer was It was 1000Ω / □ or more. Therefore, it can be seen that the diffusion preventing property by the diffusion preventing layer completely prevents the diffusion of phosphorus to the diffusion preventing layer forming surface of the semiconductor substrate.

Example 14
After the diffusion preventing layer was formed under the same printing conditions as in Example 13 using the diffusion preventing layer forming coating solution used in Example 10, “diffusion” was performed in the same manner as in Example 1.
Thereafter, the obtained semiconductor substrate was immersed in a 46 wt% hydrofluoric acid (HF) aqueous solution for 3 minutes, washed with ultrapure water, and sufficiently dried. Subsequently, as a post-treatment, the semiconductor substrate was immersed in a KOH aqueous solution (0.3 wt% (produced with ultrapure water)) for 30 seconds. In this way, after removing the PSG (phosphorus glass) layer and the diffusion prevention layer, washing with ultrapure water and drying at 150 ° C. (10 minutes) were performed (see FIGS. 1 (ii) to (iv)).

Here, the measurement results of the coating solution material (part) for forming the diffusion preventing layer, the presence or absence of post-treatment, and the surface resistance value in Examples 1 to 14 are summarized in Table 1 below.

[Comparative Example 1]
<Preparation of coating solution (β) for formation of diffusion preventing layer>
80 parts of butyl carbitol acetate, 19 parts of ethyl cellulose (manufactured by Tokyo Chemical Industry Co., Ltd., ethyl cellulose 18-22 mPa · s, 5% in Toluene + Ethanol (80:20) at 25 ° C.), and aluminum oxide fine particles (manufactured by Taimei Chemical Co., Ltd., Tymicron ™) -300) 1.0 part was added and stirred to prepare an organic solvent-based anti-diffusion layer forming coating solution (β).

Then, “application to semiconductor substrate”, “diffusion”, and “measurement of surface resistance value” were performed in the same manner as in Example 1 except that this diffusion-preventing layer forming coating solution (β) was used. .

As a result, the surface resistance of the surface of the semiconductor substrate after the diffusion treatment on which the coating solution for forming the diffusion preventing layer was not applied was 60Ω / □, but the surface resistance of the surface to which the coating solution for forming the diffusion preventing layer was applied. Varied between 60 and 1000 Ω / □. Therefore, it can be seen that this diffusion preventing layer could not sufficiently prevent the diffusion of phosphorus.

Example 15
<Preparation of boron diffusion liquid (γ)>
15 parts of modified PVA (a) was added to 42.5 parts of ultrapure water, and dissolved while heating and stirring to prepare a solution (γ1). Also, 0.5 part of 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethylene oxide adduct (Shinfin Chemical Co., Surfinol 420) is added to 40 parts of glycerin. Thus, a solution (γ2) was prepared. To this solution (γ1), 2.0 parts of boric acid was added, and further the solution (γ2) was added and stirred to prepare a boron diffusion solution (γ).

<Preparation of phosphorus diffusion liquid (δ)>
22 parts of modified PVA (a) was added to 20.5 parts of ultrapure water and dissolved while stirring under heating to prepare a solution (δ1). In addition, 40 parts of glycerin, 0.5 parts of ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 420), A solution (δ2) was prepared by adding 15 parts of SiO ₂ aqueous solution (Fujimi Incorporated, Planerlite 4101, SiO ₂ 20%, water 80%). To this solution (δ1), 2.0 parts of phosphoric acid was added, and further the solution (δ2) was added and stirred to prepare a phosphorus diffusion solution (δ).

<Application to semiconductor substrate>
Using the boron diffusion liquid (γ) prepared above, screen printing was performed on one side of a semiconductor substrate (n-type single crystal silicon, with an alkali etching texture, 156 mm square, 200 μm thickness) under the following printing conditions (FIG. 2). (Refer to formation of the dopant solution coating layer 2a shown in (i)). (Printing conditions)
Printing machine: “LS-34GX” manufactured by Neurong Seimitsu Kogyo Co., Ltd.
Squeegee: NM squeegee (Hardness: 60) manufactured by Neurong Precision Industry Co., Ltd.
Squeegee angle: 80 degrees Scraper: NM squeegee (Hardness: 60) made by Neurong Seimitsu Kogyo
Scraper angle: 86 degrees Printing pressure: 0.2 MPa
Screen version: manufactured by Tokyo Process Service Co., Ltd. Plate size: 450 mm square Mesh type: V330
Application thickness: 2 μm (after drying)
Pattern: 1mm width line x 60, 3mm pitch Printing environment: 23 ° C, 60% RH
Drying conditions: 150 ° C, 2 minutes

Next, screen printing was performed using the phosphorus diffusion liquid (δ) prepared above on the boron diffusion liquid (γ) application surface of the semiconductor substrate under the same conditions as the printing conditions for the boron diffusion liquid (γ). However, the printing position was shifted by a half pitch so as to be adjacent to the printing line of the boron diffusion liquid (γ) (see formation of the dopant solution coating layer 2b shown in FIG. 2 (i)).

Thereafter, the coating solution (α) for formation of the diffusion preventing layer used in Example 1 is applied under the same conditions as in Example 1 so as to cover the coated surfaces of the boron diffusion solution (γ) and the phosphorus diffusion solution (δ). The screen was printed on the entire surface of one side of the semiconductor substrate (see FIG. 2 (ii)).

<Diffusion>
Next, 10 semiconductor substrates on which the diffusion preventing layer is formed are placed in a jig in a horizontal tube type electric furnace at intervals of 2.5 mm, put into a 700 ° C. tube furnace, and held for 15 minutes. The temperature of the tube furnace was kept at 940 ° C. for 10 minutes, and further kept at 700 ° C. for 60 minutes. The heat treatment by the tube furnace was performed in an atmosphere with an N ₂ flow rate of 98 L / min and an O ₂ flow rate of ₂ L / min. After the heat treatment, the semiconductor substrate is taken out and immersed in a 46% hydrofluoric acid (HF) aqueous solution (prepared with ultrapure water) for 3 minutes to provide a PSG (phosphorus glass) layer, BSG (boron glass) layer, and diffusion prevention. After removing the layers, washing with ultrapure water and drying at 150 ° C. (10 minutes) were performed (see FIGS. 2 (iii) and (iv)).

<Measurement results of surface resistance>
Using a resistance measuring instrument (Mitsubishi Chemical Analytech Co., Ltd., Lorester (using a PSP probe)), the surface resistance value was measured by applying the four probes to arbitrary locations on the surface of the semiconductor substrate after the treatment. As a result, the surface resistance of the surface coated with the boron diffusion solution (boron diffusion portion) was 80Ω / □, and the surface resistance of the surface coated with the phosphorus diffusion solution (phosphorus diffusion portion) was 30Ω / □. The surface resistance of the surface of the semiconductor substrate on which neither the diffusion liquid nor the phosphorus diffusion liquid was applied and to which the coating liquid for forming the diffusion preventing layer was applied was 1000Ω / □ or more. Therefore, it can be seen that the diffusion preventing layer prevented the diffusion of phosphorus and boron to the outside and the periphery.

In the present invention, the diffusion preventing layer forming coating liquid used in the examples contains fine particles of aluminum oxide or titanium oxide, and prevents the diffusion of the dopant by the shielding effect of the fine particles. It can be said that the same result can be obtained even if this is a metal oxide fine particle composed of vanadium oxide, niobium oxide, and tantalum oxide.

In addition, although the specific form in this invention was shown in the said Example, the said Example is only a mere illustration and is not interpreted limitedly. Various modifications apparent to those skilled in the art are contemplated to be within the scope of this invention.

The coating solution for forming the diffusion preventing layer of the present invention is for preventing the diffusion of the dopant by coating it on the surface of the semiconductor substrate, has a high uniformity of the diffusion preventing performance, and can also form a coating film by screen printing or the like. Since it is excellent, it can be used widely and suitably in the field of manufacturing semiconductors and semiconductor devices.

1: Semiconductor substrate 2a: Dopant solution coating layer 2b: Dopant solution coating layer 11: Dopant diffusion layer 11a: Dopant diffusion layer 11b: Dopant diffusion layer 3: Diffusion prevention layer

Claims

An anti-diffusion layer-forming coating solution that is applied to the surface of a semiconductor substrate to prevent dopant diffusion and contains the following components (A) and (B): liquid.
(A) Polyvinyl alcohol resin.
(B) Metal oxide fine particles.
The coating solution for forming a diffusion preventing layer according to claim 1, wherein the content of the metal oxide fine particles (B) is 0.1 to 40% by weight based on the total amount of the coating solution for forming the diffusion preventing layer.
The coating solution for forming a diffusion preventing layer according to claim 1 or 2, wherein the coating solution for forming a diffusion preventing layer contains 10 to 80% by weight of water.
The coating solution for forming a diffusion preventing layer according to any one of claims 1 to 3, wherein the degree of saponification of the polyvinyl alcohol-based resin (A) is 60 to 100 mol%.
The polyvinyl alcohol resin according to any one of claims 1 to 4, wherein the polyvinyl alcohol resin (A) is a polyvinyl alcohol resin having a 1,2-diol structural unit represented by the following general formula (1). Coating solution for forming a diffusion barrier layer.
The coating solution for forming a diffusion preventing layer according to any one of claims 1 to 5, wherein the coating solution for forming a diffusion preventing layer contains an alcohol.
The diffusion-preventing layer-forming coating solution according to any one of claims 1 to 6, wherein the diffusion-preventing layer-forming coating solution contains a surfactant.
The metal oxide fine particle (B) is at least one selected from Group 4 metal oxides of the periodic table, Group 5 metal oxides of the periodic table, and Group 13 metal oxides of the periodic table. 8. A coating solution for forming a diffusion preventing layer according to any one of 1 to 7.
A method for forming a diffusion barrier layer on the surface of a semiconductor substrate by applying the diffusion barrier layer forming coating solution according to any one of claims 1 to 8 to a part of the surface of the semiconductor substrate.
A step of forming a diffusion prevention layer by applying the diffusion barrier layer forming coating solution according to any one of claims 1 to 8 to a part of the surface of the semiconductor substrate; and a step of forming a semiconductor substrate with the diffusion prevention layer. A step of diffusing a dopant on the surface and forming a surface layer portion of a semiconductor substrate on which the diffusion prevention layer is not formed as a dopant diffusion layer; a step of removing the diffusion prevention layer from the semiconductor substrate on which the dopant diffusion layer is formed; A process for producing a semiconductor substrate with a dopant diffusion layer, comprising:
A coating solution for forming a diffusion prevention layer according to any one of claims 1 to 8 is applied so as to cover a portion of the surface of the semiconductor substrate after the dopant diffusion solution is coated, A step of forming a diffusion preventing layer, a heat treatment, and a step of diffusing the dopant in the applied dopant diffusion solution into the surface layer portion of the semiconductor substrate to form a dopant diffusion layer, and the dopant diffusion layer comprising: And a step of removing the diffusion barrier layer from the formed semiconductor substrate. A method for producing a semiconductor substrate with a dopant diffusion layer, comprising:
The method for producing a semiconductor substrate with a dopant diffusion layer according to claim 10 or 11, wherein the coating liquid for forming the diffusion preventing layer is applied by screen printing.
A method for producing a solar cell comprising a semiconductor substrate with a dopant diffusion layer, wherein the semiconductor substrate with a dopant diffusion layer is formed by the production method according to any one of claims 10 to 12. The manufacturing method.