JPH07100429A - Coating of polymer solution - Google Patents

Abstract

PURPOSE:To well apply a polymer soln. without involving air bubbles by applying a solvent to a substrate having difference in level before applying the polymer soln. to the substrate. CONSTITUTION:After a copper layer is formed on a silicon wafer by sputtering, the copper layer is etched to form square punched patterns on one surface of the silicon wafer in a mesh like state to form a substrate having difference in level. A solvent being a polar non-protonic solvent is applied to the substrate having difference in level in a mist like vaporized state. A polymer soln. being a photosensitive or non-photosensitive polyimide precursor soln. is applied to the coated substrate. Thereafter, the coated substrate is heat-treated with a hot plate to form a polyimide film. As a result, a polymer film free from air bubbles can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a polymer solution which can be applied satisfactorily without entraining bubbles when the polymer solution is applied onto a stepped substrate.

[0002]

2. Description of the Related Art In general, a polymer solution is applied onto a substrate by a method such as spin coating, roll coating or dip coating. In spin coating, which is often used in the electronic device field, for example, the substrate is mounted on the substrate support of the spinner, the polymer solution is placed on the substrate, and then the substrate support is rotated at high speed to apply the polymer solution to the entire substrate. Is the way to do it. Roll coating is a method in which a substrate is placed on a coating stand of a roll coater, a polymer solution is placed on the substrate, and then the polymer solution is applied onto the substrate by a roll. The dip coating is a method of applying the substrate by immersing it in a bath containing a polymer solution and then pulling it up. In either case, the polymer solution is usually applied directly onto the substrate.

[0003]

However, when the conventional method of directly coating the polymer solution on the substrate is used,
Especially when there is a step on the base, we encountered a situation in which air bubbles were caught between the base and the polymer solution applied at the step, and the solution could not be applied well. It was also found that this phenomenon is more likely to occur as the level difference increases and the viscosity of the polymer solution increases. Such entrainment of air bubbles often does not disappear even in a polymer curing step such as heat treatment usually performed after the polymer solution coating step, and often remains in the polymer even after the polymer curing. In such a case, adverse effects such as a decrease in mechanical strength of the polymer, a non-uniform dielectric constant, and a decrease in resolution are caused.

The present invention was devised in view of the above-mentioned drawbacks of the prior art, and its object is to favorably coat a polymer solution onto a stepped substrate without entraining bubbles. The present invention relates to a method of applying a polymer solution that can be used.

[0005]

The object of the present invention is as follows.
In the method for coating the polymer solution on the lower surface, a solvent is first coated and then the polymer solution is coated, which is a method for coating the polymer solution.

The substrate in the present invention is not particularly limited, but a substrate such as a silicon wafer, an alumina substrate or a glass substrate is generally used. The present invention is particularly effective because bubbles are likely to be entrained when a polymer is applied when there is a step on the base. That is, when a pattern of, for example, a metal, a polymer, a metal oxide, a metal nitride, or a metal carbide is formed on the above-mentioned substrate (the metal here includes semiconductors such as silicon and germanium), or the substrate This is the case when it has irregularities.

The polymer solution in the present invention means a polymer melted and a polymer dissolved in a soluble solvent. Examples of the polymer include polyimide, polyamic acid, polyamic acid ester, polyamide, polyamideimide, polyester, condensation polymer of alkoxide, polyvinyl alcohol, polymethacrylic acid, and polymethylmethacrylate. The present invention is particularly effective when the viscosity of the polymer solution is high, because bubbles are likely to be entrapped during application. Among the polymer solutions preferably used in the field of electronic devices, those having a relatively high viscosity include photosensitive or non-photosensitive polyimide precursor solutions.

As the polyimide precursor solution, pyromellitic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride. , 1,2,5,6-naphthalenetetracarboxylic dianhydride, tetrabutyric dianhydride such as cyclobutanetetracarboxylic dianhydride, 4,4'-diaminodiphenyl ether, 3,3 '
A polyamic acid obtainable by reacting a diamine such as diaminodiphenyl sulfone, 4,4′-diaminodiphenylmethane, bis (3-aminopropyl) tetramethyldisiloxane, metaphenylenediamine or paraphenylenediamine in a polar aprotic solvent; Examples thereof include alcohol esters such as methyl ester, ethyl ester, and ester of 2-hydroxyethyl methacrylate, but are not limited thereto.

The photosensitive polyimide precursor is a polyamic acid having a photosensitive compound introduced therein.
Examples of the photosensitive compound used for sensitizing the polyamic acid include an acrylic ester compound, a methacrylic ester compound, an acrylamide compound, a bisazide, and an amino compound having a vinyl group.
The method of introducing the photosensitive compound is not particularly limited, and examples thereof include a method of mixing a polyamic acid and a photosensitive compound, and a method of esterifying a polyamic acid with a photosensitive alcohol. Specific examples of the composition of the photosensitive polyimide precursor include those described in JP-B-59-52822. A photosensitive polyimide precursor solution is obtained by dissolving such a photosensitive polyimide precursor in a polar aprotic solvent. Examples of commercially available products are "Photo Nice" UR-3
140, UR-5100 (manufactured by Toray) and the like.

When these polymer solutions are applied onto a substrate by a known method such as spin coating, roll coating or dip coating, the solvent is applied first, and then the polymer solution is applied. Is.

First, the solvent to be applied may be a polymer solution or a solvent which does not exert a significant influence on the polymer (precipitation, chemical change, etc.), but it is preferable that the viscosity is 25 P. It is a compound. Here, the organic compound may be one kind of organic compound or a mixture of two or more kinds of organic compounds. A preferred example is N-
Methyl-2-pyrrolidone, N, N-dimethylformamide, γ-butyrolactone, N, N-dimethylacetamide, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4,4-dimethyl-1,3
-Dioxane, 3-methylsulfolane, methylglyme, methyl diglyme, methyl triglyme, methyl tetraglyme, ethyl glyme, ethyl diglyme, butyl diglyme, ethyl cellosolve, methyl cellosolve, butyl cellosolve, butyl carbitol, propylene carbonate, 2 -Hydroxyethyl methacrylate, methyl ethyl ketone, N-methylformamide, tetrahydrothiophene, dimethylsulfoxide, sulfolane, 2-pyrrolidone, acetone, acetonitrile, ethanol, methanol, 1-propanol, 2-propanol, 2-butanol, 1,2-propanediol ,
Examples thereof include isobutyl acetate, butyl acetate, pyrrole, ethylene glycol and diethylene glycol. More preferably, it is a polar aprotic solvent. Here, the polar aprotic solvent refers to a solvent which has neither the ability to give a proton to another, nor does it undergo self-dissociation and has a dipole moment of 2.0 or more. For example N-methyl-2
-Pyrrolidone, N, N-dimethylformamide, γ-butyrolactone, N, N-dimethylacetamide, sulfolane, dimethylsulfoxide, acetone, acetonitrile, N-methylformamide and the like can be mentioned. Among these, N-methyl-2-pyrrolidone, N,
N-dimethylformamide, γ-butyrolactone, N,
N-dimethylacetamide is more preferred and most preferably the same as the solvent of the polymer solution. As described above, a polar aprotic solvent is generally used as the solvent for the polymer solution.

The method of applying these solvents is not particularly limited, but it is preferable to apply them in a liquid state, a mist state or a vapor state.

To apply the solvent in a mist state means to apply the solvent in the form of fine droplets onto the base. The droplet diameter is preferably 1 mm or less. More preferably 0.
It is 1 mm or less. The method of applying in a mist state is not particularly limited, and examples thereof include a method of discharging a solvent through a commercially available spray nozzle. The application in the vapor state refers to the application in which the solvent is vaporized into vapor and the vapor is liquefied when it comes into contact with the base. The method of applying in a vapor state is not particularly limited, and examples thereof include a method of exposing the substrate to a system filled with a solvent vapor.

[0014]

【Example】

Example 1 15 μm on a silicon wafer by sputtering
After the copper layer is formed, the copper layer is etched by using the photoresist as a mask to form a square-shaped blank pattern having a side of 100 μm in a mesh shape at 20 μm intervals on the entire surface of the substrate.
A stepped base was obtained. Next, N-methyl-2-pyrrolidone was applied on the substrate in a liquid state at 400 rpm for 10 seconds by a spinner. Subsequently, 4,4′-diaminodiphenyl ether and pyromellitic dianhydride are reacted in an N-methyl-2-pyrrolidone solvent in an equimolar ratio, and N, N
′ -Diethylaminoethyl methacrylate was added to 4,4′-
Using a polyimide precursor solution synthesized by adding twice the molar amount of diaminodiphenyl ether, coating was performed at 2000 rpm for 30 seconds. After that, heat treatment was performed on a hot plate at 80 ° C. for 20 minutes, and subsequently, heat treatment was performed at 350 ° C. for 1 hour to form a polyimide film.

As a result of observing the polyimide film thus obtained with an optical microscope, no bubbles were observed in the polyimide film.

Comparative Example 1 A polyimide film was formed in the same manner as in Example 1 except that the solvent was not applied to the mesh-shaped pattern and the polyimide precursor solution was applied directly. As a result of observing the polyimide film thus obtained with an optical microscope, many bubbles were observed.

Example 2 A polyimide film was formed in the same manner as in Example 1 except that γ-butyrolactone was applied on the mesh pattern.

As a result of observing the polyimide film thus obtained with an optical microscope, no bubbles were observed in the polyimide film.

Example 3 Example 1 was the same as Example 1 except that N, N-dimethylformamide was coated on the mesh pattern.
A polyimide film was formed in the same manner as in.

As a result of observing the polyimide film thus obtained with an optical microscope, no bubbles were observed in the polyimide film.

Example 4 Example 1 is the same as Example 1 except that N, N-dimethylacetamide was coated on the mesh pattern.
A polyimide film was formed in the same manner as in.

As a result of observing the polyimide film thus obtained with an optical microscope, no bubbles were observed in the polyimide film.

Example 5 Example 1 is the same as Example 1 except that N-methyl-2-pyrrolidone was applied in a mist state using a spray.
A polyimide film was formed in the same manner as in.

As a result of observing the polyimide film thus obtained with an optical microscope, no bubbles were observed in the polyimide film.

[0025]

According to the coating method of the present invention, it is possible to solve the problem of entrainment of air bubbles when a polymer solution is applied onto a base having a step, and to obtain a polymer film having no bubbles. . Therefore, problems such as a decrease in mechanical strength of the polymer, a non-uniform dielectric constant, and a decrease in resolution can be solved.

Claims (9)

[Claims] 1. A method of coating a polymer solution on a substrate, which comprises first coating a solvent and then coating the polymer solution. 2. The method for applying a polymer solution according to claim 1, wherein the polymer solution is applied onto a base having a step. 3. The method for applying a polymer solution according to claim 1, wherein the polymer solution is a photosensitive or non-photosensitive polyimide precursor solution. 4. The method for coating a polymer solution according to claim 1, wherein the solvent to be coated is a polar aprotic solvent. 5. The polar aprotic solvent is N-methyl-2-
The method for applying a polymer solution according to claim 4, which is pyrrolidone, N, N-dimethylformamide, γ-butyrolactone or N, N-dimethylacetamide. 6. The method of coating a polymer solution according to claim 1, wherein the solvent to be coated is the same solvent as the solvent of the polymer solution. 7. The method for applying a polymer solution according to claim 1, wherein the solvent to be applied is applied in a mist state. 8. The method for applying a polymer solution according to claim 1, wherein the solvent to be applied is applied in a vapor state. 9. The method for applying a polymer solution according to claim 1, wherein the polymer solution is applied by spin coating.