JP4541243B2 - Boron diffusion coating solution - Google Patents

Description

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

  For the manufacture of transistors, diodes, ICs and the like, silicon semiconductor devices having a P-type region in which boron is diffused are used. As a method of diffusing boron in the silicon semiconductor device, there are a pyrolysis method, a counter NB method, a dopant host method, a coating method, etc., among others, boron 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 coating methods, a method of applying a boron-containing coating solution 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, a diffusion coating solution containing basically a dopant source such as a boron compound, a water-soluble polymer, and water is known (for example, see Patent Documents 1 and 2). 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

  An object of the present invention is to provide a coating solution for boron diffusion which can diffuse boron at a high concentration without variation in resistance value of a semiconductor device 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 boron compound, (B) a water-soluble polymer compound, and (C) water, and has a viscosity at 20 ° C. of 500 to 100,000 mPa · s. Exists in the coating solution.

  (A) Boron compound, (B) Water-soluble polymer compound, (C) Water is blended and the viscosity at 20 ° C. is set to 500 to 100,000 mPa · s. A coating solution for boron diffusion capable of diffusing and fixing boron at a high concentration without variation in value can be provided.

  The boron diffusion coating solution of the present invention contains (A) a boron 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 blending amount of other blending components. In addition, the viscosity of the conventionally known coating liquid for diffusion (for example, Patent Documents 1 and 2 above) was as low as 50 to 60 cp (50 to 60 mPa · s).

The boron compound (A) refers to a material that can satisfy a supply concentration of boron and can produce a liquid having good stability. As such a boron compound (A), specifically, boric acid (H ₃ BO ₃ ), Anhydrous boric acid (B ₂ O ₃ ), ammonium tetraborate (hydrate), alkyl borate ester and boron chloride. Of these, boric acid (H ₃ BO ₃ ) and boric anhydride (B ₂ O ₃ ) are more preferable because boron can be supplied at a high concentration with a small amount of use.

  The content of the boron compound (A) in the boron diffusion coating solution is preferably 0.3 to 10% by weight, more preferably 0.5 to 5% by weight in the coating solution. When the content of the boron compound (A) is less than 0.3% by weight, the amount of boron supply decreases, and the expected resistance value of the semiconductor device tends not to be obtained. Moreover, when content of a boron compound (A) exceeds 10 weight%, there exists a tendency for stability of coating liquid, such as precipitation of a boron compound, to be impaired.

  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 alternating 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. When the average degree of polymerization is less than 200, the viscosity of the coating solution for boron diffusion becomes low, so that the coating film becomes thin, and therefore the supply amount of boron tends to be insufficient. On the other hand, when the average degree of polymerization of polyvinyl alcohol is larger than 8000, the viscosity becomes too high and bubbles tend to be generated at the time of coating, or the resistance value of the semiconductor device varies due to insufficient leveling, which tends to be undesirable.

  In addition, in any of the above, there are many restrictions on the supply amount of the boron compound, and it becomes difficult to match the target resistance value of the semiconductor device.

  The average degree of polymerization referred to here is a value calculated from the relative viscosity with water by measuring the viscosity of the aqueous solution using an Ostwald viscometer after completely saponifying polyvinyl alcohol based on JIS K6726. .

  The saponification degree of polyvinyl alcohol is preferably 50 mol% or more, and more preferably 60 to 100 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 coating solution for boron diffusion is preferably 5 to 25% by weight and more preferably 7 to 20% by weight in the coating solution. When the content of the water-soluble polymer compound (B) is less than 5% by weight, the viscosity of the coating solution tends to be low, and thus the supply amount of boron tends to be insufficient. On the other hand, when the content of the water-soluble polymer compound (B) exceeds 25% by weight, the viscosity of the coating solution tends to be too high, and the resistance value of the semiconductor device tends to vary due to insufficient leveling.

  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 boron 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 (D) is less than 25% by weight, the viscosity becomes too high and bubbles are generated during coating, or the resistance value of the semiconductor device varies due to insufficient leveling, which tends to be undesirable. On the other hand, when the content of water (D) exceeds 85% by weight, the viscosity tends to be too low and the coating film becomes a thin film, and the boron supply amount tends to be insufficient, which tends to be undesirable.

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

  The water-miscible organic solvent (D) has a boiling point of 100 ° C. or higher and is excellent in affinity 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 tends to be too fast 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 speed of the coating film is decreased, so that the productivity is decreased or the thickness unevenness tends to occur due to the decrease in the coating film surface strength in the drying process. Absent.

  Examples of the water-miscible organic solvent (D) include ethylene glycol derivatives, diethylene glycol derivatives, propylene glycol derivatives and the like.

  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-nbutyl 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), diethylene glycol derivatives are preferred because the solubility of the boron compound is high and the leveling time is easily obtained due to the low vapor pressure. Among these, the solubility of the boron compound is preferred. Diethylene glycol monomethyl ether is preferred because of its high water solubility.

  The content of the water-miscible organic solvent (D) in the boron diffusion coating solution is preferably 4 to 65% by weight and 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 the dissolution stability of the boron compound and the drying delay 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 alcoholic hydroxyl group-containing polymer compound such as polyvinyl alcohol becomes unstable, and the liquid stability may be impaired.

  The content of the water-miscible organic solvent (D) in the boron diffusion coating solution is preferably 300 parts by weight or less, more preferably 250 parts by weight or less, and 200 parts by weight 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 boron 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 active because impurities such as alkali metals and heavy metals are not introduced into semiconductor devices. Agents are preferred. In addition, examples of nonionic surfactants include silicon surfactants, fluorine surfactants, and hydrocarbon surfactants. However, hydrocarbon surfactants are more quickly activated by firing during overheating such as diffusion. Agents are preferred.

  Examples of the hydrocarbon-based surfactant include block copolymers of ethylene oxide-propylene oxide, acetylene glycol compounds, and the like. However, acetylene glycol compounds are more preferable because variations in resistance values of semiconductor devices are further reduced. .

  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 coating solution for boron diffusion is preferably 0.1 to 10% by weight, and more preferably 0.5 to 5% by weight in the coating solution. When the content of the surfactant (E) is less than 0.1% by weight, the antifoaming effect expected tends to be poor. Further, when the content of the surfactant (E) exceeds 10% by weight, the stability of the coating solution for boron 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 liquid are not impaired. For example, a compound capable of forming an N-type region is blended for the purpose of adjusting the diffusion concentration to the wafer. can do. Examples of compounds that can form such an N-type region include, but are not limited to, phosphorus compounds such as phosphoric anhydride, phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

  The boron diffusion coating solution of the present invention comprises a boron 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, It is prepared by mixing the surfactant (E). In that case, after preparing the aqueous solution containing water-soluble compound (B) and water (C), boron compound (A) is mixed with this, and also water miscible organic solvent (D) and surfactant (E). And a method of mixing a boron compound (A) and a water-miscible organic solvent (D) in advance to prepare a solution, and mixing this with an aqueous solution of the water-soluble compound (B). Although it is mentioned, it is not limited to these.

  The viscosity of the coating solution for boron diffusion of the present invention at 20 ° C. is 500 to 100,000 mPa · s, preferably 600 to 50000 mPa · s, more preferably 700 to 30000 mPa · s, and still more preferably 1000 to 10,000 mPa · s. If the viscosity of the coating solution for boron diffusion is less than 500 mPa · s, the fluidity is too high and a uniform coating film cannot be obtained at the time of coating film formation, or a thick film cannot be formed. Diffusing high concentration boron becomes difficult. On the other hand, when the viscosity of the boron diffusion coating solution exceeds 100,000 mPa · s, it is difficult to cause bubbles during formation of the coating film, or the leveling is insufficient, which causes variations in the resistance values of the semiconductor devices. In addition, the viscosity of the coating liquid for boron diffusion at 20 ° C. can be obtained by measuring with a Brookfield viscometer manufactured by Brookfield.

  The P-type diffusion layer of silicon semiconductor is a step of applying the boron 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 3) for the purpose of doping boron onto the wafer.

  As the coating method of the boron diffusion coating solution 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 step 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 resistivity of the P-type diffusion surface of the obtained silicon semiconductor device can be 0.1 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 to 4 and Comparative Examples 1 and 2
<Preparation of boron diffusion coating solution>
Example 1
85 g of PVA (average polymerization degree: 500, saponification degree: 88 mol%) was dissolved in 320 g of ultrapure water to prepare a solution A.

  Further, 15 g of boric acid was dissolved in 205 g of diethylene glycol monomethyl ether (boiling point: 192 ° C.) to prepare a solution B.

  Then, the solutions A and B were mixed, and further 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate (in the general formula (1), m + n≈1.3) 10 g Was added to prepare a boron diffusion coating solution (opaque, white liquid) of Example 1.

  The content of boric acid in the prepared coating solution for boron diffusion is 2.4% by weight, the content of PVA is 13.4% by weight, the content of diethylene glycol monomethyl ether is 32.3% by weight, and the content of water is The content of ethoxylated product of 50.3% by weight and 2,4,7,9-tetramethyl-5-decyne-4,7-diol was 1.6% by weight.

Example 2
In Example 1, a coating solution for boron diffusion was prepared in the same manner as in Example 1 except that the average degree of polymerization of PVA was 800, the saponification degree was 71 mol%, and the amount used was 70 g.

  In the prepared boron diffusion coating solution, the content of boric acid is 2.4% by weight, the content of PVA is 11.3% by weight, the content of diethylene glycol monomethyl ether is 33.1% by weight, and the content of water is The content of ethoxylated product of 51.6% by weight and 2,4,7,9-tetramethyl-5-decyne-4,7-diol was 1.6% by weight.

Example 3
In Example 1, a coating solution for boron diffusion was prepared in the same manner as in Example 1 except that the average polymerization degree of PVA was 1400, the saponification degree was 78 mol%, and the amount used was 50 g.

  The content of boric acid in the prepared boron diffusion coating solution is 2.5% by weight, the content of PVA is 8.3% by weight, the content of diethylene glycol monomethyl ether is 34.2% by weight, and the content of water is The content of the ethoxylated product of 53.3% by weight and 2,4,7,9-tetramethyl-5-decyne-4,7-diol was 1.7% by weight.

Example 4
In Example 1, a coating solution for boron diffusion was prepared in the same manner as in Example 1 except that the average degree of polymerization of PVA was 500, the saponification degree was 71 mol%, the amount used was 70 g, and boric acid was 30 g. did.

  The boric acid content in the prepared boron diffusion coating solution is 4.7% by weight, the PVA content is 11.0% by weight, the diethylene glycol monomethyl ether content is 32.3% by weight, and the water content is The content of ethoxylated product of 50.4% by weight and 2,4,7,9-tetramethyl-5-decyne-4,7-diol was 1.6% by weight.

Comparative Example 1
85 g of PVA (average polymerization degree: 100, saponification degree: 88 mol%) was dissolved in 320 g of ultrapure water to prepare a solution C.

  Further, 15 g of boric acid was dissolved in 205 g of diethylene glycol monomethyl ether (boiling point: 192 ° C.) to prepare a solution D.

  Then, the solutions C and D are mixed, and further 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate (in the general formula (1), m + n≈1.3) 10 g Was added to prepare a boron diffusion coating solution (opaque, white liquid) of Comparative Example 1.

  The content of boric acid in the prepared coating solution for boron diffusion is 2.4% by weight, the content of PVA is 13.4% by weight, the content of diethylene glycol monomethyl ether is 32.3% by weight, and the content of water is The content of ethoxylated product of 50.3% by weight and 2,4,7,9-tetramethyl-5-decyne-4,7-diol was 1.6% by weight.

Comparative Example 2
9.3 g of PVA (weight average molecular weight: 300, degree of saponification: 88 mol%) was dissolved in 73.7 g of ultrapure water to prepare solution E.

  Further, 1.8 g of boric anhydride was dissolved in 113.4 g of propylene glycol monomethyl ether (boiling point: 120 ° C.) to prepare a solution F.

  Then, solutions E and F were mixed, and finally 0.01 g of a silicone surfactant (SH30PA manufactured by Toray Silicone Co., Ltd.) was added to prepare a boron diffusion coating solution of Comparative Example 2.

  The boric anhydride content in the diffusion coating solution of Comparative Example 2 is 0.9% by weight, the PVA content is 4.7% by weight, the propylene glycol monomethyl ether content is 57.2%, and water is contained. The amount was 37.2% by weight, and the content of the silicone surfactant was 0.005% by weight.

<Viscosity of boron diffusion coating solution>
Brookfield B-type viscometer, rotor: No. 5, the viscosity of the boron diffusion coating solution was measured under the condition of 23 ° C. at a rotation speed of 50 rpm. Table 1 shows the viscosities of the boron diffusion coating liquids of Examples 1 to 5 and Comparative Examples 1 and 2.
<Coating and diffusion on silicon semiconductor wafer>
A screen printer and a polyester # 380 mesh were used on a P-type silicon wafer (thickness: 200 μm, size: 4 inches) having a specific resistance of 10 to 20 Ω · cm temporarily fixed on a 13-inch glass. Using the boron diffusion coating liquids of Examples 1 to 5, screen printing was performed so that the coating thickness was 1.0 to 1.5 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, after putting into an electric furnace and raising the temperature from room temperature to 1200 ° C. and maintaining at 1200 ° C. for 6 hours, the temperature was lowered to room temperature to diffuse boron.

  By the above production method, a uniform diffusion film could be formed on the silicon semiconductor wafer from the boron diffusion coating solutions of Examples 1 to 4. When the surface resistivity was measured at 20 points within the surface of the diffusion film using a resistance measuring instrument (manufactured by Napson, main body: RT-8A, measuring instrument: RG-7A), 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, although an attempt was made to produce a diffusion film from the boron diffusion coating liquids of Comparative Examples 1 and 2 by the above production method, a uniform diffusion film could not be formed.

Claims (5)

(A) a boron compound, (B) a water-soluble polymer compound include (C) water, and (E) a surfactant, Ri viscosity 500~100000mPa · s der at 20 ° C.,
Wherein the surfactant (E) acetylene glycol compound der Ru boron diffusion coating solution of the following general formula (1).

(In the 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 each satisfy 0-30) The boron compound (A) is at least one selected from the group consisting of boric acid, anhydrous boric acid, ammonium tetraborate hydrate, alkyl borate ester, and boron chloride. Coating liquid for diffusion. The coating solution for boron diffusion according to claim 1 or 2, wherein the water-soluble polymer compound (B) is polyvinyl alcohol. Furthermore, the coating liquid for boron diffusion of Claim 1, 2, or 3 containing the water miscible organic solvent (D) whose boiling point is 100 degreeC or more. 5. The boron diffusion coating solution according to claim 4, wherein the water-miscible organic solvent (D) is a diethylene glycol derivative.