JP2007053353A - Phosphorus-diffusing coating liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphorus-diffusing coating liquid which can diffuse phosphorus in a high concentration without variation of resistance of a semiconductor device on a large wafer of 4 inch or more. <P>SOLUTION: The phosphorus-diffusing coating liquid contains (A) phosphorus compound, (B) water-soluble high polymer compound, and (C) water, and its viscosity at 20°C is 500-100,000 mPa s. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel phosphorus diffusion coating solution, and more particularly to a novel phosphorus diffusion coating solution for diffusing phosphorus on the surface of a silicon semiconductor.

  In the manufacture of transistors, diodes, ICs, etc., silicon semiconductor devices having an N-type region in which phosphorus is diffused are used. As a method of diffusing phosphorus in the silicon semiconductor device, there are a thermal decomposition method, a counter NB method, a dopant host method, a coating method, etc., among which a phosphorus can be uniformly diffused without requiring an expensive apparatus. Furthermore, since it is excellent in mass productivity, the coating method is suitable. In particular, among the coating methods, a method of coating a coating solution containing phosphorus using a spin coater is employed. Recently, in order to reduce the manufacturing cost, a conventional wafer having a size of 3 inches or less is shifting to a large wafer having a size of 4 inches or more. In this case, application by spin coating is suitable for a wafer of 3 inches or less, but when applied to a large wafer of 4 inches or more, there is a disadvantage that the film thickness becomes non-uniform. Therefore, a screen printing method has been studied as a new coating method.

  As a diffusion coating solution, basically, a diffusion coating solution containing a dopant source such as a phosphorus compound, a water-soluble polymer, and water is known (for example, see Patent Documents 1 to 5). However, even when this conventional coating liquid for diffusion is applied as it is to the screen printing method, the viscosity is extremely low, the printing surface is not stable, and quick drying is high and continuous printing is impossible. There is a problem that it is difficult to form.

JP-A-5-347265 JP 2002-75893 A JP 2002-75894 A Japanese Patent Laid-Open No. 2003-218048 JP 2003-218049 A

  An object of the present invention is to provide a phosphorus diffusion coating solution that can diffuse phosphorus in a high concentration without variation in resistance of semiconductor devices even when a large wafer of 4 inches or more is manufactured by screen printing. And

  The present inventor has found that the object of the present invention can be achieved by adjusting the viscosity of the coating liquid to a specific range as a result of examination in view of the above circumstances, and has completed the present invention.

  That is, the gist of the present invention includes (A) a phosphorus compound, (B) a water-soluble polymer compound, and (C) water, and has a viscosity at 20 ° C. of 500 to 100,000 mPa · s. It exists in the coating liquid for diffusion.

  By blending (A) a phosphorus compound, (B) a water-soluble polymer compound, and (C) water and setting the viscosity at 20 ° C. to 500 to 100000 mPa · s, the semiconductor device can be formed on a large wafer of 4 inches or more. It is possible to provide a phosphorus diffusion coating solution capable of diffusing and fixing phosphorus at a high concentration without variation in resistance value.

  The coating solution for phosphorus diffusion of the present invention contains (A) a phosphorus compound, (B) a water-soluble polymer compound, and (C) water, and has a viscosity at 20 ° C. of 500 to 100,000 mPa · s.

  The viscosity of the coating solution in the present invention can be adjusted mainly by the selection and concentration of the water-soluble polymer compound to be used, and the type and amount of other compounding components. In addition, the viscosity of a conventionally known diffusion coating solution of the same type (for example, Patent Documents 1 to 5 above) was as low as 50 to 60 cp (50 to 60 mPa · s).

The phosphorus compound (A) refers to one that can satisfy the supply concentration of phosphorus and can produce a liquid having good stability. Examples of such phosphorus compound (A) include phosphoric anhydride (phosphorus pentoxide), phosphorus It is preferably at least one selected from the group consisting of an acid (H ₃ PO ₄ ), ammonium dihydrogen phosphate, and diammonium hydrogen phosphate. Among these, anhydrous phosphoric acid (diphosphorus pentoxide P ₂ O ₅ ) or phosphoric acid (H ₃ PO ₄ ) is more preferable from the viewpoint that the phosphorus element can be supplied at a high concentration.

  The content of the phosphorus compound (A) in the coating solution for phosphorus diffusion is preferably 10 to 70% by weight and more preferably 15 to 60% by weight in the coating solution. Furthermore, 20 to 50% by weight is more preferable. If the content of the phosphorus compound (A) is less than 10% by weight, the amount of phosphorus element supplied decreases, so that sufficient diffusion cannot be obtained and the expected resistance value tends not to be achieved. Moreover, when content of a phosphorus compound (A) exceeds 70 weight%, there exists a tendency for the solubility of a water-soluble polymer compound to fall.

  Examples of the water-soluble polymer compound (B) include vinyl polymer compounds such as polyvinyl alcohol, polyvinyl imidazole, polyvinyl pyrrolidone and polyvinyl caprolactam, polyethylene oxide, polypropylene oxide, and alternate or block copolymers of polyethylene oxide-polypropylene oxide. Cellulose polymers such as polyalkylene oxide compounds, polyhydroxymethyl acrylate, polyhydroxyethyl acrylate, polyhydroxypropyl acrylate, or polyhydroxyalkyl acrylates or methacrylates such as methacrylates, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, etc. A compound etc. can be mentioned. The water-soluble polymer compound (B) can be used alone or in combination of two or more. Of these, polyvinyl alcohol is desirable from the viewpoint of effectiveness and is the most typical.

  When using polyvinyl alcohol, the selection of the degree of polymerization and the degree of saponification is important. The viscosity of the coating solution can be finely adjusted by selecting these physical properties and using them. 200-8000 are preferable, as for the average degree of polymerization of polyvinyl alcohol, 300-3000 are more preferable, and 300-2600 are more preferable. If the average degree of polymerization is less than 200, the viscosity of the coating solution for phosphorus diffusion is greatly reduced, so that the coating film becomes a thin film, and therefore the supply amount of phosphorus tends to be insufficient. On the other hand, if the average degree of polymerization exceeds 8000, the viscosity tends to be too high and bubbles are generated at the time of coating, or the resistance value of the semiconductor device varies due to insufficient leveling, which tends to be undesirable. The average degree of polymerization of the polyvinyl alcohol is a value calculated from the relative viscosity with water after measuring the viscosity of the aqueous solution using an Ostwald viscometer after completely saponifying the polyvinyl alcohol based on JIS K 6726. is there.

  The saponification degree of polyvinyl alcohol is preferably 50 mol% or more, and more preferably 60 to 99.99 mol%. When the saponification degree is less than 50 mol%, the solubility of polyvinyl alcohol is lowered, and it is difficult to form a uniform coating solution, which is inappropriate.

  Polyvinyl alcohol is a polymer obtained mainly by saponifying a polymer of vinyl acetate with an alkali or an acid, and is not particularly limited. Moreover, you may have functional groups, such as a carboxylic acid group, a quaternary ammonium group, and an acetoacetate group, in the side chain.

  Furthermore, as the polyvinyl alcohol, a saponified product of a copolymer of vinyl acetate and a monomer having vinyl acetate and vinyl acetate can be used.

  Examples of such monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, vinylene carbonates, acrylic acid, methacrylic acid, crotonic acid, maleic acid, and maleic anhydride. , Unsaturated acids such as itaconic acid or salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, etc. Olefin sulfonic acid or its salt, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethyldiallylammonium chloride, dimethylali Polyoxyalkylene (meth) allyl ethers such as vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, polyoxyethylene (meth) acrylate, poly Polyoxyalkylene (meth) acrylates such as oxypropylene (meth) acrylate, polyoxyethylene (meth) acrylamide, polyoxyalkylene (meth) acrylamides such as polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) (Acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene amine Triethanolamine, polyoxyethylene vinyl amine, polyoxypropylene vinyl amine.

  Furthermore, mention may be made of a method of reacting polyvinyl alcohol and diketene, a method of reacting polyvinyl alcohol and acetoacetate and transesterifying, a method of copolymerizing vinyl acetate and vinyl acetoacetate, and the like. However, in order to obtain acetoacetylated polyvinyl alcohol having a simple manufacturing process and good quality, it is preferable to manufacture by a method of reacting polyvinyl alcohol (powder) and diketene. As a method of reacting polyvinyl alcohol and diketene, polyvinyl alcohol and gaseous or liquid diketene may be reacted directly, or after an organic acid is adsorbed and occluded in advance in polyvinyl alcohol, it is gaseous in an inert gas atmosphere. Alternatively, a method of spraying and reacting liquid diketene, or spraying and reacting a mixture of an organic acid and liquid diketene with polyvinyl alcohol is used.

  As a reaction apparatus for carrying out the above reaction, an apparatus that can be heated and has a stirrer is sufficient. For example, a kneader, a Henschel mixer, a ribbon blender, other various blenders, and a stirring and drying apparatus can be used.

  The content of the water-soluble polymer compound (B) in the phosphorus diffusion coating solution is preferably 3 to 25% by weight, more preferably 5 to 20% by weight in the coating solution. If the content of the water-soluble polymer compound (B) is less than 3% by weight, the viscosity of the coating solution tends to be low, and therefore the phosphorus supply amount tends to be insufficient. On the other hand, if the content of the water-soluble polymer compound (B) exceeds 25% by weight, the viscosity becomes so high that bubbles are generated at the time of coating or the resistance value of the semiconductor device varies due to insufficient leveling. Tend.

  As the water (C), ultrapure water, ion exchange water, or distilled water is used, and ultrapure water is particularly preferable. Among these, the smaller the amount of impurity elements such as alkali metals and heavy metal elements and foreign matters in water, the better.

  The content of water (C) in the phosphorus diffusion coating solution is preferably 25 to 85% by weight, and more preferably 35 to 65% by weight in the coating solution. If the content of water (C) is less than 25% by weight, the viscosity becomes so high that bubbles are generated at the time of coating, or the resistance value of the semiconductor device varies due to insufficient leveling, which tends to be undesirable. On the other hand, if the content of water (C) exceeds 85% by weight, the viscosity tends to be too low, the coating film becomes thin, and the amount of phosphorus supplied tends to be insufficient.

  The phosphorus diffusion coating solution of the present invention preferably further contains a water-miscible organic solvent (D).

  The water-miscible organic solvent (D) refers to a solvent having a boiling point of 100 ° C. or higher and excellent miscibility with water.

  The boiling point of the water-miscible organic solvent (D) is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, and further preferably 170 ° C. or higher. When the boiling point of the water-miscible organic solvent is less than 100 ° C., drying is too early and sufficient leveling cannot be expected. Further, the boiling point of the water-miscible organic solvent is preferably 270 ° C. or less, and more preferably 230 ° C. or less. When the boiling point of the water-miscible organic solvent exceeds 270 ° C., the drying rate of the coating film decreases, so that the productivity tends to decrease or thickness unevenness tends to occur due to a decrease in coating film surface strength during the drying process.

  Examples of the water-miscible organic solvent (D) include diethylene glycol derivatives, ethylene glycol derivatives, propylene glycol derivatives, other polyhydric alcohol compounds and derivatives thereof.

  Specific examples of the diethylene glycol derivative include diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, and the like.

  Specific examples of the ethylene glycol derivative include ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol mono-n-butyl ether.

  Specific examples of the propylene glycol derivative include propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-butyl ether and the like.

  Other polyhydric alcohol compounds and derivatives thereof include 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, glycerin and the like And derivatives thereof.

  Of the water-miscible organic solvents (D), a diethylene glycol derivative is preferred because it is highly water-soluble and has a low vapor pressure so that sufficient time for leveling can be obtained. Among them, diethylene glycol monomethyl ether is preferred.

  The content of the water-miscible organic solvent (D) in the coating solution for phosphorus diffusion is preferably 4 to 65% by weight, more preferably 10 to 40% by weight in the coating solution. When the content of the water-miscible organic solvent (D) is less than 4% by weight, there is a tendency that a sufficient addition effect cannot be obtained with respect to leveling due to delayed drying of the coating film. On the other hand, when the content of the water-miscible organic solvent (D) exceeds 65% by weight, the solubility of the water-soluble polymer compound such as polyvinyl alcohol becomes unstable and the liquid stability tends to be impaired.

  The content of the water-miscible organic solvent (D) in the phosphorus diffusion coating solution is preferably 300 parts by weight or less, more preferably 250 parts by weight or less, with respect to 100 parts by weight of water (C). Part or less is more preferable, and 150 parts by weight or less is particularly preferable. When the content of the water-miscible organic solvent (D) exceeds 300 parts by weight with respect to 100 parts by weight of water (C), the solubility of the water-soluble polymer compound (B) decreases and precipitates from the coating solution. Since there are cases, it is not preferable.

  The phosphorus diffusion coating agent of the present invention preferably further contains a surfactant (E). Examples of surfactants include nonionic surfactants, cationic surfactants, and anionic surfactants, but nonionic surfactants are less likely to introduce alkali metal and heavy metal impurities into semiconductor devices. Is preferred. Examples of nonionic surfactants include silicon surfactants, fluorine surfactants, hydrocarbon surfactants, etc., but hydrocarbon surfactants are rapidly fired during heating in the diffusion process. Agents are preferred. Furthermore, examples of the hydrocarbon surfactant include ethylene oxide-propylene oxide block copolymers, acetylene glycol compounds, and the like, and among them, acetylene glycol compounds are more preferable.

  As the acetylene glycol compound, those represented by the following general formula (1) are preferable.

In General Formula (1), R ² and R ³ each represent an alkyl group having 1 to 3 carbon atoms, R ¹ and R ⁴ each represent an alkyl group or an allyl group having 1 to 20 carbon atoms, and m and n satisfies 0-30, respectively.

  The number of moles of ethylene oxide units added in the acetylene glycol compound represented by the general formula (1) is preferably 0 ≦ m + n ≦ 30 [mol]. When the total number of added moles of ethylene oxide exceeds 30 moles, the solubility in water is increased and the foaming properties are increased, so that the defoaming effect tends to be lowered.

  Examples of the acetylene glycol compound represented by the general formula (1) include 2,5,8,11-tetramethyl-6-dodecin-5,8-diol, 5,8-dimethyl-6-dodecin-5,8- Diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 4,7-dimethyl-5-decyne-4,7-diol, 2,3,6,7-tetramethyl- Examples include 4-octyne-3,6-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 2,5-dimethyl-3-hexyne-2,5-diol.

Moreover, as an ethoxylated form of the acetylene glycol compound of the general formula (1), for example, an ethoxylated form of 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol (total number of moles of ethylene oxide added: 6), 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate (total number of moles of ethylene oxide added: 10), 2,4,7,9-tetramethyl-5- Ethoxylated form of decyne-4,7-diol (total number of moles of added ethylene oxide: 4), ethoxylated form of 3,6-dimethyl-4-octyl-3,6-diol (total number of moles of added ethylene oxide: 4) An ethylene oxide derivative of acetylene glycol such as 2,4,7,9-tetramethyl-5-decyne-4,7-dio is particularly preferable. Polyoxy Le (moles of ethylene oxide added Total: 1.3, the general formula (1) in which R ¹ and R ⁴ are iso- butyl group, R ² and R ³ is a methyl group, m + n = 1.3), 2 , 4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate (total number of moles of ethylene oxide added: 3.5, in formula (1), R ¹ and R ⁴ are iso-butyl groups , R ² and R ³ are methyl groups, m + n = 3.5).

  Surfactant (E) can be used alone or in combination of two or more.

  The content of the surfactant (E) in the phosphorus diffusion coating solution is preferably 0.1 to 10% by weight, more preferably 0.3 to 8% by weight, and 0.5 to 5% by weight in the coating solution. Further preferred. When the content of the surfactant (E) is less than 0.1% by weight, the antifoaming effect expected tends to be poor. On the other hand, if the content of the surfactant (E) exceeds 10% by weight, the stability of the coating solution for phosphorus diffusion such as layer separation tends to become unstable.

  The coating solution for phosphorus diffusion of the present invention can further contain silica (F). Examples of the silica (F) used in the present invention include colloidal silica, amorphous silica, and fumed silica. Colloidal silica is preferably used. By compounding silica (F), the diffusion concentration of phosphorus in the phosphorus diffusion coating solution can be improved. Examples of the shape of the silica (F) include a spherical shape, a granular shape, a powder shape, and a bead shape.

  Moreover, 0.001-50 micrometers is preferable, as for the average particle diameter of a silica (F), 0.005-30 micrometers is more preferable, and 0.005-20 micrometers is further more preferable. If the particle size is less than 0.001 μm, the fluidity of the coating solution may be lowered. Conversely, if the particle size exceeds 50 μm, the stability of the coating solution tends to be lowered.

  The surface of silica (F) may be cationized with an organic substance or an inorganic substance.

  The content of silica (F) in the coating solution for phosphorus diffusion is preferably 0.5 to 20% by weight, more preferably 1.0 to 20% by weight in the coating solution. When the content of silica (F) is less than 0.5% by weight, the expected improvement in diffusion efficiency tends not to be obtained. On the other hand, when the content of silica (F) exceeds 20% by weight, the stability of the coating solution for phosphorus diffusion such as layer separation tends to become unstable.

  In the present invention, if necessary, various additives can be blended as long as the basic physical properties of the coating solution are not impaired. For example, a compound capable of forming a P-type region is blended for the purpose of adjusting the diffusion concentration to the wafer. can do. Examples of compounds that can form such a P-type region include boron compounds such as boric acid, anhydrous boric acid, ammonium tetraboron, alkylborates, and boron chloride, and aluminum compounds such as aluminum hydroxide, aluminum sulfate, and aluminum nitrate. However, it is not limited to these.

  The coating solution for phosphorus diffusion of the present invention comprises a phosphorus compound (A), a water-soluble polymer compound (B) and water (C), preferably a water-miscible organic solvent (D) having a boiling point of 100 ° C. or higher, an interface It is produced by mixing the activator (E) and silica (F). In that case, an aqueous solution containing the water-soluble polymer compound (B) and water (C) is prepared, and then the phosphorus compound (A) is mixed therewith, and the water-miscible organic solvent (D), surfactant ( E), a method in which silica (F) is added and mixed, or a phosphorus compound (A) and a water-miscible organic solvent (D) are mixed in advance to prepare a solution, and an aqueous solution of this and the water-soluble compound (B) The water-soluble compound (B) is dissolved in an aqueous dispersion containing silica (F) and water (C), and this is mixed with the phosphorus compound (A) and the water-miscible organic solvent (D). Although the method of mixing the solution to contain is mentioned, It is not limited to these.

  The viscosity of the coating solution for phosphorus diffusion of the present invention at 20 ° C. is 500 to 100,000 mPa · s, preferably 1000 to 50000 mPa · s, more preferably 2000 to 30000 mPa · s, and further preferably 2000 to 20000 mPa · s. If the viscosity of the coating solution for phosphorus diffusion is less than 500 mPa · s, the fluidity is too high, a uniform coating film cannot be obtained at the time of coating film formation, or a thick film cannot be formed, and the phosphorus supply amount is insufficient. Diffusing high concentration phosphorus becomes difficult. On the other hand, if the viscosity of the coating solution for phosphorus diffusion exceeds 100,000 mPa · s, it is not preferable that bubbles are hardly broken at the time of coating film formation or the leveling is insufficient, resulting in variations in the resistance value of the semiconductor device. In addition, the viscosity of the coating liquid for phosphorus diffusion at 20 ° C. was measured using a B type viscometer (programmable viscometer RVDV-II +) manufactured by Brookfield Co. 5. This is a value measured at a rotation speed of 50 rpm. If the test torque value deviates from 10% to 90% of the measurable range under the conditions depending on the coating solution, it is measured by adjusting the rotation speed within that range as appropriate. do it.

  The N-type diffusion layer of silicon semiconductor is a step of applying the phosphorus diffusion coating solution of the present invention on a wafer and drying it (hereinafter referred to as step 1), and 90% or more of the organic components in the coating film remaining in step 1 It is formed through a baking step (hereinafter referred to as step 2) for the purpose of removing hydrogen, and then a diffusion step (hereinafter referred to as step 2) for the purpose of doping the wafer with phosphorus.

  As the coating method of the phosphorus diffusion coating liquid in step 1, screen printing method, gravure printing method, relief printing method, planographic printing method, spin coater method, comma coater method, die head coater method, die lip coater method and gravure printing method Any of these may be applied, but the coating liquid of the present invention is preferably applied to screen printing. As a result, coatings with various film thicknesses can be uniformly printed on wafers of 4 inches or more, particularly 4 to 6 inches or more.

  As a drying method in the step 1, it is preferable to dry at a temperature of 20 to 300 ° C. for 1 to 60 minutes.

  The firing step in step 2 is preferably performed by continuous firing of a temperature profile having a maximum temperature (300 to 1000 ° C.).

  In the diffusion process of step 3, the wafer after step 2 is maintained at a high temperature (800 to 1400 ° C.) for a desired time in an electric furnace or the like with a single wafer or a plurality of stacked wafers. It means spreading on the surface.

  It should be noted that step 1 and step 2 may be performed continuously as necessary, and step 3 may be omitted when a desired resistance value is obtained in step 2.

  The surface resistance of the N-type diffusion surface of the obtained silicon semiconductor device can be set to 0.03 to 10000Ω / □.

  Examples of the present invention will be described below. The scope of the present invention is not limited by the examples.

Examples 1-5 and Comparative Examples 1-3
<Preparation of coating solution for phosphorus diffusion>
Example 1
100 g of ultrapure water and 20 g of PVA powder (average degree of polymerization 1,400, degree of saponification: 78 mol%) were dissolved while heating as necessary to prepare solution A.

  Further, 45 g of diethylene glycol monomethyl ether (boiling point: 192 ° C.) and ethoxylated product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (in the general formula (1), m + n≈1.3 ) 3 g was added to make solution B.

Then, 100 g of an aqueous phosphoric acid solution (phosphoric acid for EL manufactured by Kanto Chemical Co., Inc .: 85% by weight H ₃ PO ₄ , 15% by weight of water) is added to the solution A, and the solution B is further added and stirred. The phosphorus diffusion coating liquid (opaque, white liquid) of Example 1 was prepared.

In the prepared phosphorous diffusion coating solution, the content of phosphoric acid (H ₃ PO ₄ ) is 31.7% by weight, the content of PVA is 7.5% by weight, the content of diethylene glycol monomethyl ether is 16.8% by weight, water The content of was 42.9% by weight, and the content of ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol was 1.1% by weight.

Example 2
In a mixed solution of 70 g of ultrapure water and 50 g of colloidal silica aqueous solution (Snowtex O-40 manufactured by Nissan Chemical Industries, Ltd., silica 40 wt%, water 60 wt%), PVA powder (average polymerization degree 1,400, 20 g of saponification degree: 78 mol%) was dissolved while heating as necessary to prepare Solution C.

  Further, 30 g of diethylene glycol monomethyl ether (boiling point: 192 ° C.) and ethoxylated product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (in the general formula (1), m + n≈1.3 ) 7 g was added to make solution D.

Then, 100 g of phosphoric acid aqueous solution (phosphoric acid for EL manufactured by Kanto Chemical Co., Inc .: 85% by weight H ₃ PO ₄ , 15% by weight of water) is dissolved in the solution C, and further, the solution D is added and stirred. The phosphorus diffusion coating liquid (opaque, white liquid) of Example 2 was prepared.

In the prepared phosphorous diffusion coating solution, the content of phosphoric acid (H ₃ PO ₄ ) is 30.7% by weight, the content of PVA is 7.2% by weight, the content of diethylene glycol monomethyl ether is 10.8% by weight, The content of water is 41.6 wt%, the content of silica is 7.2 wt%, and the content of ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol is 2.5% by weight.

Example 3
In a mixed solution of 120 g of ultrapure water and 50 g of colloidal silica aqueous solution (Snowtex O-40, 40% by weight of silica, 60% by weight of water manufactured by Nissan Chemical Industries, Ltd.), PVA powder (average polymerization degree 500, saponification) Degree: 88 mol%) 50 g was dissolved while heating as necessary to prepare solution E.

  Further, 30 g of diethylene glycol monomethyl ether (boiling point: 192 ° C.) and ethoxylated product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (in the general formula (1), m + n≈1.3 ) 7 g was added to make Solution F.

Then, 100 g of an aqueous phosphoric acid solution (phosphoric acid for EL manufactured by Kanto Chemical Co., Inc .: 85% by weight H ₃ PO ₄ , 15% by weight of water) is dissolved in the solution E, and the solution F is added and stirred. The phosphorus diffusion coating liquid (opaque, white liquid) of Example 3 was prepared.

The phosphorous acid (H ₃ PO ₄ ) content in the prepared phosphorous diffusion coating solution is 23.8% by weight, the PVA content is 14.0% by weight, the diethylene glycol monomethyl ether content is 8.4% by weight, The content of water is 46.2% by weight, the content of silica is 5.6% by weight, and the content of ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol Was 2.0% by weight.

Example 4
PVA powder (average polymerization degree 2400, saponification) in a mixed solution of 120 g of ultrapure water and 25 g of colloidal silica aqueous solution (Snowtex O-40 manufactured by Nissan Chemical Industries, Ltd., silica 40 wt%, water 60 wt%) Degree: 80.5 mol%) 15 g was dissolved while heating as necessary to prepare solution G.

  Further, 15 g of diethylene glycol monomethyl ether (boiling point: 192 ° C.) and ethoxylated product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (in the general formula (1), m + n≈1.3 ) 5 g was added to make solution H.

Then, 120 g of phosphoric acid aqueous solution (phosphoric acid for EL manufactured by Kanto Chemical Co., Inc .: 85% by weight H ₃ PO ₄ , 15% by weight of water) is dissolved in the solution G, and the solution H is added and stirred. The phosphorus diffusion coating liquid (opaque, white liquid) of Example 4 was prepared.

The content of phosphoric acid (H ₃ PO ₄ ) in the prepared phosphorus diffusion coating solution is 34.0% by weight, the content of PVA is 5.0% by weight, the content of diethylene glycol monomethyl ether is 5.0% by weight, The content of water is 51.0% by weight, the content of silica is 3.3% by weight, and the content of ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol Was 1.7% by weight.

Example 5
Necessary 40 g of PVA powder (average polymerization degree 1400, saponification degree: 78 mol%) in 200 g of colloidal silica aqueous solution (Snowtex O, manufactured by Nissan Chemical Industries, Ltd., silica 20 wt%, water 80 wt%) Accordingly, the solution was dissolved while heating to prepare Solution I.

  Further, 100 g of diethylene glycol monomethyl ether (boiling point: 192 ° C.) and ethoxylated product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (in the general formula (1), m + n≈1.3 ) 12 g was added to make Solution J.

Then, 100 g of an aqueous phosphoric acid solution (phosphoric acid for EL manufactured by Kanto Chemical Co., Inc .: 85% by weight H ₃ PO ₄ , 15% by weight of water) is added to the solution I, and the solution J is further added and stirred. The phosphorus diffusion coating liquid (opaque, white liquid) of Example 5 was prepared.

In the prepared phosphorous diffusion coating solution, the content of phosphoric acid (H ₃ PO ₄ ) is 18.8% by weight, the content of PVA is 8.8% by weight, the content of diethylene glycol monomethyl ether is 22.1% by weight, The content of water is 38.8% by weight, the content of silica is 8.8% by weight, and the content of ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol Was 2.7% by weight.

Example 6
PVA powder (average degree of polymerization: 1,400) in a mixed solution of 70 g of ultrapure water and 50 g of colloidal silica aqueous solution (Snowtex O-40 manufactured by Nissan Chemical Industries, Ltd., silica 40 wt%, water 60 wt%) , Saponification degree: 78 mol%) was dissolved while heating as necessary to prepare Solution X.

  Further, 30 g of diethylene glycol monomethyl ether (boiling point: 192 ° C.) and ethoxylated product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (in the general formula (1), m + n≈1.3 ) 20 g was added to make Solution Y.

Then, 100 g of an aqueous phosphoric acid solution (phosphoric acid for EL manufactured by Kanto Chemical Co., Inc .: 85% by weight H ₃ PO ₄ , 15% by weight of water) is dissolved in the solution X, and the solution Y is further added and stirred. The phosphorus diffusion coating liquid (opaque, white liquid) of Example 6 was prepared.

The phosphorous acid (H ₃ PO ₄ ) content in the prepared phosphorous diffusion coating solution is 29.3% by weight, the PVA content is 6.9% by weight, the diethylene glycol monomethyl ether content is 10.3% by weight, The content of water is 39.7% by weight, the content of silica is 6.9% by weight, and the content of ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol is It was 6.9% by weight.

Comparative Example 1
100 g of ultrapure water and 20 g of PVA powder (average polymerization degree 100, saponification degree: 78 mol%) were dissolved while heating as necessary to prepare solution K.

  Further, 45 g of diethylene glycol monomethyl ether (boiling point: 192 ° C.) and ethoxylated product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (in the general formula (1), m + n≈1.3 ) 3 g was added to make solution L.

Then, 100 g of phosphoric acid aqueous solution (EL phosphoric acid for EL: 85 wt% H ₃ PO ₄ , 15 wt% of water manufactured by Kanto Chemical Co., Ltd.) is added to the solution K, and the solution L is further added and stirred. The phosphorus diffusion coating liquid (opaque, white liquid) of Example 1 was prepared.

In the prepared phosphorous diffusion coating solution, the content of phosphoric acid (H ₃ PO ₄ ) is 31.7% by weight, the content of PVA is 7.5% by weight, the content of diethylene glycol monomethyl ether is 16.8% by weight, water The content of was 37.3% by weight, and the content of ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol was 1.1% by weight.

  The weight ratio (C / D) of water to diethylene glycol monomethyl ether was 69/31.

Comparative Example 2
Organic silicate binder (HAS-1 manufactured by Colcoat Co., Ltd., 25 ° C. viscosity: 6 mPa · S, effective silica content: 10% by weight, ethanol: 78% by weight) 90 g, anhydrous phosphoric acid (diphosphorus pentoxide) 10 g Was dissolved little by little to prepare a phosphorus diffusion coating solution of Comparative Example 2.

The content of phosphoric anhydride (P ₂ O ₅ ) in the prepared phosphorus diffusion coating solution was 10% by weight, and the content of silica was 10% by weight.

Comparative Example 3
7 g of PVA powder (average polymerization degree 500, saponification degree: 88 mol%) was added to 30 g of ultrapure water, and 15 g of 2-propanol was further added to prepare Solution M.

  Further, 10 g of ammonium dihydrogen phosphate was added to 40 g of ultrapure water, and the mixture was stirred until it was uniform to prepare Solution N.

  Then, the solution N was gradually added to the solution M and stirred to prepare the phosphoric acid diffusion coating liquid (transparent liquid) of Comparative Example 3.

  In the prepared phosphorous diffusion coating solution, the content of ammonium dihydrogen phosphate is 9.8% by weight, the content of PVA is 6.9% by weight, and the content of water is 68.6% by weight. 0.7% by weight.

  And the solution I was gradually added to the solution H, and the phosphorus diffusion coating liquid of the comparative example 3 was produced.

<Viscosity of phosphorus diffusion coating solution>
Using a Brookfield B-type viscometer (programmable viscometer RVDV-II +), the rotor no. The viscosity of the phosphorus diffusion coating solution was measured at 5, 50 rpm. Table 1 shows the viscosities of the coating solutions for diffusing phosphoric acid of Examples 1 to 5 and Comparative Examples 1 to 3.

<Coating and diffusion on silicon semiconductor wafer>
A screen printer and a polyester # 380 mesh were used on an N-type silicon wafer (thickness: 200 μm, size: 4 inches) having a specific resistance of 10 to 20 Ω · cm temporarily fixed on 13-inch glass. Using the phosphorus diffusion coating liquids of Examples 1 to 5, screen printing was performed so that the coating thickness was 3.0 to 3.5 μm.

  Next, the wafer was dried in a dryer set at 100 ° C. for 30 minutes and then baked in a continuous baking furnace having a maximum temperature of 580 ° C. and a temperature profile through a deashing process at 380 to 400 ° C. Then, it was put into an electric furnace, heated from room temperature to 1200 ° C. and maintained at 1200 ° C. for 12 hours, and then the temperature was lowered to room temperature to diffuse phosphorus.

  By the above production method, a uniform diffusion film could be formed on the silicon semiconductor wafer from the phosphorous diffusion coating liquids of Examples 1 to 5. Using a resistance measuring instrument (manufactured by Napson Corporation, main body: RT-8A, measuring instrument: RG-7A), the surface resistance was measured at 20 points within the surface of the diffusion film, and the variation was small. Table 1 shows the maximum value, the minimum value, and the difference between the surface resistance values.

  On the other hand, production of a diffusion film was attempted from the phosphorous diffusion coating liquids of Comparative Examples 1 to 3 by the above production method, but a uniform diffusion film could not be formed.

Claims (7)

A coating solution for phosphorus diffusion, comprising (A) a phosphorus compound, (B) a water-soluble polymer compound, and (C) water, and having a viscosity at 20 ° C. of 500 to 100,000 mPa · s. The phosphorus compound (A) is at least one selected from the group consisting of anhydrous phosphoric acid (diphosphorus pentoxide), phosphoric acid (H ₃ PO ₄ ), ammonium dihydrogen phosphate and diammonium hydrogen phosphate. The coating liquid for phosphorus diffusion according to claim 1, wherein The coating solution for phosphorus diffusion according to claim 1 or 2, wherein the water-soluble polymer compound (B) is polyvinyl alcohol. Furthermore, the coating liquid for phosphorus diffusion of Claim 1, 2, or 3 containing the water miscible organic solvent (D) whose boiling point is 100 degreeC or more. The coating liquid for phosphorus diffusion according to claim 4, wherein the water-miscible organic solvent (D) is a diethylene glycol derivative. Furthermore, surfactant (E) is contained, The coating liquid for phosphorus diffusion of Claim 1, 2, 3, 4 or 5 characterized by the above-mentioned. Furthermore, the coating liquid for phosphorus diffusion of Claim 1, 2, 3, 4, 5 or 6 characterized by containing a silica (F).