Cleaning and liquid contact with solids – Processes – For metallic – siliceous – or calcareous basework – including...
Reexamination Certificate
1999-02-23
2003-05-27
Kelly, Cynthia H. (Department: 1774)
Cleaning and liquid contact with solids
Processes
For metallic, siliceous, or calcareous basework, including...
C510S169000, C510S171000, C510S407000, C510S505000, C510S108000, C510S201000
Reexamination Certificate
active
06569251
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a cleaner for lithography which is used for dissolving or removing a resist etc. and in particular to a cleaner for lithography which can be used usefully to clean a coater such as in a coater cup, to remove an unnecessary resist from a substrate when or after coating of a resist, to remove the resist from the substrate after the object using the resist was achieved, and to clean or rinse the substrate after removal of the resist.
BACKGROUND OF THE INVENTION
For production of integrated circuit elements, color filters, liquid crystal display elements, etc., lithography using resists are conventionally used. For example, in production of integrated circuit elements etc. by use of lithography, an anti-reflective coating is formed as necessary on a substrate, then a positive- or negative-working resist is applied thereto, the solvent is removed by baking, an anti-reflective coating is formed as necessary on the resist layer which is then exposed to ultraviolet rays, deep ultraviolet rays, electron beams, X-rays, etc., followed baking as necessary and development to form a resist pattern. Thereafter, baking is conducted as necessary, and the substrate is subjected to etching etc., and the resist is generally removed.
For coating of the resist, various methods such as spin coating method, roller coating method, reverse roller coating method, cast coating method, doctor coating method, dip coating method, etc. are used. For example, in production of integrated circuit elements, spin coating method is mainly used as a method of coating a resist. In spin coating method, a resist solution is dropped on a substrate, and due to the rotation of the substrate, this dropped resist solution is cast in the direction toward the outer periphery of the substrate so that an excess of the resist solution is removed by scattering from the outer periphery of the substrate, whereby a resist layer having a desired film thickness is formed. A part of the excess resist remains in a coater cup and solidified with time as the solvent is evaporated. The solidified material becomes fine powder which is then scattered to adhere to the substrate, thus causing resist pattern defects. To prevent this phenomenon, it is necessary to clean the coater cup every a few to dozens of substrates. Further, in the case where a resist layer having a desired thickness is formed by spin coating method on the substrate, there is the disadvantage that a part of the resist solution moves further to the back of the substrate, or the resist solution remains thickly (i.e. beads are formed) on the outer periphery of the substrate, and therefore it is necessary to remove the unnecessary resist or the beads from the side, the outer periphery or the back of the substrate. Further, even in other coating methods than spin coating method, adhesion of a resist to an improper portion occurs as is the case with spin coating. After the substrate is subjected to etching etc., the resist is generally removed and even in this removal step, the resist is dissolved and removed usually by means of an organic solvent.
The surface of the substrate from which the resist was removed by dissolution is made contaminant-free by generally cleaning using purified water etc., thus removing fine particles remaining on the surface of the substrate, followed by the subsequent step. If the solvent used for removal of the resist is a water-insoluble organic solvent or an amine type organic solvent, the substrate is often rinsed with a clean, water-soluble organic solvent rather than cleaning with purified water immediately after the step of removing the resist. The reason for this is that if a water-insoluble organic solvent is used as the liquid for removal of the resist, the resist dissolved in this solvent is prevented from adhering again to the substrate by preventing it from being precipitated in the solvent upon mixing with purified war, and that the water-insoluble organic solvent present on the surface of the substrate is once replaced by a water-soluble organic solvent to facilitate replacement by purified water. If an amine type organic solvent is used as the liquid for removal of the resist, this solvent remains in purified water to make it alkaline whereby the metallic substrate is prevented from corroding.
After the coating step is finished, the coater should be cleaned for subsequent use or as a coater used again for other materials, or if an anti-reflective coating is resent between the substrate and the resist layer, the anti-reflective coating may be removed with a solvent as necessary after the resist pattern is formed.
As described above, a cleaner is used in various steps in lithography process, and as this cleaner, a wide variety of cleaners consisting of organic solvents are known (e.g. Japanese Patent Application Publication No. 4-49938).
However, some conventional cleaners require much time or should be used in a large amount because of their poor ability to dissolve the resist and some are very toxic, so there is no cleaner satisfying both excellent solvent properties and safety to the human body, and therefore there is strong demand for a cleaner satisfying both solvent properties and safety to the human body. Although the production of integrated circuit elements has been described above, the above description applies not only to the production of integrated circuit elements but also to the production of color filters, liquid crystal elements, etc.
The object of the present invention is to provide a cleaner for lithography which is free of the aforementioned problems, that is, a cleaner which can be used usefully to clean a coater such as in a coater cup, to remove an unnecessary resist from a substrate when or after coating of a resist, to remove the resist from the substrate after the object using the resist was achieved, to clean and rinse the substrate after removal of the resist, which has a high solubilizing agility to permit sufficient cleaning to be effected rapidly in a small amount of the cleaner, and which is highly safe to he human body.
DISCLOSURE OF THE INVENTION
As a result of their eager research, the present inventor found that the above object can be achieved by using a homogeneous mixture of specific organic solvents and specific alcohols as a cleaner for lithography, to work out the present invention.
That is, the present invention relates to a cleaner for lithography which comprises a homogeneous solution comprising at least one selected from highly safe organic solvents of Group A below and at least one selected from alcohols having alkyl group with 1 to 4 carbon atoms.
Group A
propylene glycol alkyl ether
propylene glycol alkyl ether acetate
ethylene glycol alkyl ether
ethylene glycol alkyl ether acetate
acetic acid alkyl ester
propionic acid alkyl ester
alkoxypropionic acid alkyl ester
lactic acid alkyl ester
aliphatic ketone
alkoxybutanol
Another present invention relates to a cleaner for lithography which comprises a homogeneous solution comprising propylene glycol alkyl ether and at least one alcohol selected from alcohols having alkyl group with 1 to 4 carbons.
A further present invention relates to a cleaner for lithography which comprises a homogeneous solution comprising propylene glycol alkyl ether and at least one alcohol selected from alcohols having alkyl group with 1 to 4 carbons, wherein the propylene glycol alkyl ether is at least one selected from propylene glycol monomethyl ether, propylene glycol monoethyl ether and propylene glycol monopropyl ether, and the alcohol is at least one selected from ethanol, 1-propanol and 2-propanol.
An additional present invention relates to a cleaner for lithography which comprises a homogeneous solution comprising propylene glycol alkyl ether acetate and at least one alcohol selected from alcohols having alkyl group with 1 to 4 carbons.
Another further present invention relates to a cleaner for lithography which comprises a homogeneous solution comprising propylene glycol alkyl ether acetate and at least o
Banerjee Krishna
Clariant Finance (BVI) Limited
Garrett Dawn
Jain Sangya
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