Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2001-02-16
2002-09-24
Webb, Gregory E. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S176000, C510S212000, C134S001300, C134S002000, C134S003000, C438S669000, C438S745000
Reexamination Certificate
active
06455479
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of removal of polymeric materials from a substrate. In particular, the present invention relates to compositions and methods for the removal of residues left behind after plasma etch and ash process of silicon wafers used in manufacturing electronic devices.
Numerous materials containing polymers are used in the manufacture of electronic devices, such as circuits, disk drives, storage media devices and the like. Such polymeric materials are found in photoresists, solder masks, antireflective coatings, and the like. During manufacture of such electronic devices, the polymeric material is subjected to special processes and treatment conditions such as halogen or halide plasma etch, auto-plasma ash processing, reactive ion etching and ion milling that cause extensive cross-linking of the photoresist polymer and make the removal of such cross-linked polymeric material extremely difficult.
For example, modern technology utilizes positive-type resist materials for lithographically delineating patterns onto a substrate so that the patterns can be subsequently etched or otherwise defined into the substrate material. The resist material is deposited as a film and the desired pattern is defined by exposing the resist film to energetic radiation. Thereafter the exposed regions are subject to a dissolution by a suitable developer liquid. After the pattern has been thus defined in the substrate the resist material must be completely removed from the substrate to avoid adversely affecting or hindering subsequent operations or processing steps.
It is necessary in such a photolithographic process that the photoresist material, following pattern delineation, be evenly and completely removed from all unexposed areas so as to permit further lithographic operations. Even the partial remains of a resist in an area to be further patterned is undesirable. Also, undesired resist residues between patterned lines can have deleterious effects on subsequent processes, such as metallization, or cause undesirable surface states and charges.
Plasma etching, reactive ion etching and ion milling are required as the geometry of features get smaller and pattern density increases. During the plasma etch process, a photoresist film forms a hard to remove organometallic polymeric residue on the side walls of the various features being etched. Furthermore, the photoresist is extensively cross-linked due to the high vacuum and high temperature conditions in the etch chamber. Known cleaning processes do not acceptably remove such polymeric residue. For example, acetone or N-methylpyrrolidone is used at extreme conditions, which include high temperature and extended cycle times. Such use conditions are often above the flash point of the solvent which has certain environmental, health and safety issues regarding operator exposure. In addition, productivity and throughput are adversely affected by the extended process cycle times required. Even with such extreme stripping conditions, the devices typically need manual “swabbing”, or brushing, to remove tenacious “rabbit ear”-type polymeric residue from the fine features.
In recent years, the semiconductor manufacturing industry has moved to dry plasma etching processes of metal and oxide layers in order to achieve the desired features with sub-half micron geometry. As a result, the need for photoresist and polymer removers that work effectively without damaging the integrity of fine feature microcircuit lines has drastically increased. Known photoresist removal or stripping formulations that typically contain strong alkaline solutions, organic polar solvents or strong acids and oxidizing agents are no longer applicable for those cross-linked polymers. Typical organic polar solvents used in conventional stripping formulations include pyrrolidones such as N-methylpyrrolidone, N-ethylpyrrolidone, N-hydroxyethylpyrrolidone and N-cyclohexylpyrrolidone; amides including dimethylacetamide or dimethylformamide; phenols and derivatives thereof. Such solvents have been used in combination with amines or other alkaline components that are effective in photoresist stripping. These compositions are not effective in post plasma polymer removal applications.
Recently, aqueous mixtures of hydroxylamine and alkanolamines along with different chelating agents have been used. For example, U.S. Pat. No. 5,334,332 (Lee) discloses compositions for removing etching residue containing 5 to 50% hydroxylamine, 10 to 80% of at least one alkanolamine and water. U.S. Pat. No. 4,401,747 (Ward et al.) discloses a stripping composition containing 30 to 90% 2-pyrrolidone and 10 to 70% dialkyl sulfone. Also, U.S. Pat. No. 5,795,702 (Tanabe et al.) discloses a stripping composition that contains 2 to 30% of hydroxylamine, 2 to 20% of an amine, 35 to 80% of a water soluble organic solvent in water with 2 to 20% of a corrosion inhibitor.
The above described compositions may be effective on typical Al/Si wafers that contain titanium nitride (“TiN”) as cap layers and barrier layers, however, they are not applicable to 100% copper devices, or devices with high percentage of copper and low dielectric constant (“low-k”) dielectric materials. These compositions are also corrosive to other corrosion sensitive alloys, such as tungsten, gallium or gallium arsenide, that are mainly used in modem chip manufacturing technology. Soft metals, such as copper and tungsten, are easily corroded by any hydroxylamine containing materials. Further, the strong tendency of copper for complex formation with hydroxylamine makes using such products undesirable for 100% copper or alloys having high copper content.
In addition, known stripping compositions containing hydroxylamine have numerous other drawbacks including, undesirable flammability, explosion hazard, toxicity, volatility, odor, instability at elevated process temperatures such as up to 80° to 90° C., and high cost due to handling such regulated materials. A particular problem with advanced devices, such as magnetic thin film heads for disk drives and storage media devices, is that known stripping compositions are incompatible with a variety of thin films in such devices, that is, conventional stripping compositions cause corrosion of the thin metal layers, particularly copper, and low-k dielectric material present in such advanced devices.
Furthermore, industrial grade hydroxylamine free base has high ionic contamination that cannot be used for electronic applications. Further purification is therefore necessary to convert the technical grade material to an electronic grade product. Purification of hydroxylamine free base via distillation processes has recently caused several fatal explosions, making handling of such high purity material extremely dangerous.
U.S. Pat. No. 5,988,186 (Ward et al.) discloses stripping compositions having at least about 10% by weight water, a water soluble polar solvent, an organic amine and gallic acid or a gallic acid ester. This patent does not disclose a combination of a polyhydric alcohol and a polar organic solvent.
U.S. Pat. No. 5,561,105 (Honda) discloses a photoresist stripping composition including an organic polar solvent having a dipole moment of more than 3.5; an amine compound selected from compounds having a certain formula, an a chelating reagent comprising a mono- or poly-valent acid ligand covalently bonded to a polymeric or oligomeric backbone. This patent does not disclose polyhydric alcohols, nor compositions free of an acid-type ligand.
There is thus a continuing need for strippers that effectively remove polymeric material, are more environmentally friendly, are less dangerous to manufacture and do not cause corrosion of the substrate, particularly thin metal films and the dielectric layers in the substrate.
SUMMARY OF THE INVENTION
It has been surprisingly found that polymeric material may be easily and cleanly removed from substrates, particularly 100% copper substrates and thin film heads for disk drives and storage media devices. Such polymeric
Cairns S. Matthew
Shipley Company L.L.C.
Webb Gregory E.
LandOfFree
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