Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
2001-01-17
2003-10-21
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C134S002000, C134S026000, C134S027000, C134S028000, C134S029000, C134S038000, C134S040000, C134S902000, C438S905000, C510S175000, C510S176000, C510S178000, C510S420000, C510S421000, C510S424000, C510S425000, C510S426000, C510S427000, C510S428000, C510S435000
Reexamination Certificate
active
06635118
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to the aqueous cleaning of spin coating bowl assemblies employed in microelectronic fabrication processes. This invention is particularly concerned with the cleaning of photoresist, polyimide and other polymers from spin coating bowl assemblies with water based detergent compositions as an environmentally friendly replacement of organic solvents that are commonly used for cleaning photoresist and polyimide residue from polymer film application equipment. The invention is also applicable to cleaning low dielectric constant polymer dielectric residue from spin coating bowls and associated equipment for coatings on device wafers and on ceramic substrates.
In semiconductor device fabrications, formation of thin polymer films of photoresist, antireflective coatings, polyimide-polyamic acid precursor, and low dielectric constant polymer dielectric materials (low-k materials) such as Silk (Dow trade name), and siloxane based materials such as silsesquioxane and hydrogen silsesquioxane (HSQ) polymers on various substrates by the spin coating technique is an important part of the process sequence. Various solvents used in film coating formulations of these polymers include: propyleneglycol methylether acetate (PGMEA), cyclohexanone, ethoxyethyl propionate (EEP), ethyl lactate, methyl isobutyl ketone (MIBK), n-methylpyrrolidinone (NMP), gama-butyrolactone, aromatic hydrocarbons and mixture thereof. The spin coating equipment includes a coating bowl assembly made of a machined teflon top shield, a stainless steel plate, and a bottom teflon bowl. The substrate, silicon wafer or ceramic substrate to be coated is positioned on a vacuum chuck in the center of the bowl where it is held in place by vacuum during spinning. A small volume of the polymer solution is dispensed in the center of the substrate and spun at a pre-determined spin speed and time duration. In this operation, excess polymer solution which may be a photoresist, typically comprising a phenolic resin of the type novolak or poly (p-hydroxystyrene) as matrix resins and a photoactive compound, acid-amplified resists, antireflective coating formulation, polyimide-polyamic acid coating formulation, or low-k polymer materials, splashes against the inside walls of the spin coating bowl and other assembly parts. Although most of the excess polymer drains into a receptacle from where it is later removed, a fraction of the splashed material remains adhered to the spin coater walls and associated assembly parts. With repeated use of the spin coating bowl assembly, the polymer builds up inside the coater bowl and the assembly parts to several hundred microns which, if not removed, can flake off causing contamination on the film surface, film defects and consequently product yield loss. Therefore, it is essential to clean the spin coating bowl assembly every 100 to 200 hours of use to prevent the possibility of film defects caused by falling debris of dry polymer residue.
At present, throughout the microelectronic industry, the resist coating bowls and associated equipment are cleaned with organic solvents, typically, 1-methyl-2-pyrrolidinone (NMP), n-butyl acetate (nBA), acetone, isopropanol (IPA), methyl isobutylketone (MIBK) and dimethylacetamide (DMAC). As such organic solvents may present environmental problems, it is necessary to install specialized abatement equipment to control air emissions. In addition to environmental problems, IPA, nBA, MIBK and acetone are highly flammable solvents having flash point<100° F. and thus present a fire hazard, which requires costly explosion-proof equipment for their use.
There are a number of methods proposed by others for the stripping and cleaning of photoresist and polyimide residues. Nishi, Japanese Patent number 08104895, the disclosure of which is incorporated by reference herein, discloses the use of diacetone alcohol for cleaning photoresist based on quinonediazide-novolak.
Sugyama, Japanese Patent number 08165495, the disclosure of which is incorporated by reference herein, discloses a solvent system comprising a mixture of 1-methyl-2-pyrrolidinone and/or N, N-dimethylacetamide, and alkylene glycol monoalkyl ethers for cleaning polyimide precursor residues in semiconductor manufacturing.
Walsh et al. U.S. Pat. No. 5,698,045, the disclosure of which is incorporated by reference herein, discloses a method for removing polymer residue from chemical processing equipment according to which the contaminated surface is exposed to vapors of NMP such that the vapors from the boiling solvent condense on the polymer surface causing the polymer to flake-off.
Notwithstanding the prior art, major problems with the cleaning solvents for photoresist and polyimide residues disclosed in the art are chemical safety, and environmental concerns. Thus, a purpose of the present invention is to have a method for providing suitable water-based cleaning alternatives along with the necessary cleaning equipment for aqueous cleaning processes.
Accordingly, it is a purpose of this invention to provide an environmentally friendly water-based cleaning method for cleaning polymer residues of photoresist, antireflective coatings, siloxane containing polymers, polyimide, spin-on low k interlevel dielectric polymer and the like from spin coating bowl assemblies and replace organic solvents such as NMP, IPA, acetone, nBA, MIBK, diacetone alcohol etc., which are traditionally used for cleaning polymer residue from various surfaces in semiconductor device manufacturing.
It is another purpose of this invention to provide water-based detergent formulations for spin coater bowl assembly cleaning employing a combination of surfactants in conjunction with alkali, alkanolamine, and alkali metal salt of dibasic/polybasic organic acid.
It is another purpose of this invention to provide a polymer coater bowl cleaning unit assembly and method for spin coater bowl assembly cleaning with aqueous detergent formulations employing ultrasonic cleaning and a dishwasher rinse cycle.
It is another purpose of this invention to provide aqueous cleaning solutions for polymer processing equipment in semiconductor manufacturing using water solution of surface tension lowering agents in conjunction with alkali metal hydroxides, or tetraalkyammonium hydroxide, alkanolamine, and combinations thereof.
It is another purpose of this invention to provide a method for aqueous cleaning of spin coater bowl assembly and related polymer processing equipment.
It is another purpose of this invention to provide an aqueous cleaning method for polymer spin coating equipment using water-based alkaline solutions which have no problem of volatile air emissions, no chemical safety or flammability issues, and which does not require high cost cleaning equipment.
These and other purposes of the present invention will become more apparent after referring to the following description considered in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
This invention is concerned with spin coater bowl assembly cleaning to remove polymer residue of photoresists, antireflective coatings, polyimide precursor coatings, and the low dielectric constant polymers from the spin coating bowl side walls and assembly parts. Particularly, this invention is concerned with replacement of NMP and flammable solvents with water-based cleaning solutions to provide an environmentally friendly option for cleaning spin coating bowl assemblies. This invention is especially concerned with aqueous alkaline cleaning compositions and method of using the same for cleaning polymer spin coating bowls and associated assembly parts to remove polymer residues from coating formulations of photoresists, antireflective coatings, acid-amplified resists, silicone-containing polymers, polyimide-precursor formulations, as well as spin-on low-k materials based on hydrogen silsesquioxane (HSQ), FOx flowable oxide, and related silsesquioxane polymers.
The inventors have discovered that water-based alkaline detergent solutions comprising a
Capogna Gerard V.
Cormack Richard A.
Mancaruso Felice J.
Sachdev Harbans S.
Sachdev Krishna
Cioffi James J.
Gulakowski Randy
Kornakov M.
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