Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2000-02-25
2003-03-11
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C134S002000, C510S254000, C510S255000
Reexamination Certificate
active
06531436
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally 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 polymeric material from 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 conditions that make the removal of such polymeric material 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.
In fabrication of magnetic thin film heads (“TFH”) for disk drive and data storage media devices, photoresists are commonly applied on a variety of thin films as masking agents for precision design of magnetoresistive and giant magnetoresistive heads. Although the photolithography and reactive ion etches used resemble semiconductor processes, these sliders, i.e. magnetoresistive (“MR”) or giant magnetoresistive (“GMR”) heads, are built in the millions of units, on aluminum titanium carbide (“AlTiC”) ceramic wafers. Common thin films associated with magnetoresistive heads include aluminum oxide (“Al
2
O
3
”), gold (“Au”), cobalt (“Co”), copper (“Cu”), iron (“Fe”), iridium (“Ir”), manganese (“Mn”), molybdenum (“Mo”), nickel (“Ni”), platinum (“Pt”), ruthenium (“Ru”), and zirconium (“Zr”). These films are completely different from those found in integrated circuit semiconductor fabrication which include predominantly aluminum (“Al”), tungsten (“W”), titanium (“Ti”), and silicon oxides as the interlayer dielectrics.
Within the last five years the technology for storage media has grown exponentially and has driven slider performance through miniaturization and higher area density which today exceeds 20 Gb/in
2
. In order to keep at pace with next generation technology, read-write head manufacturers are utilizing advanced photoresists and multi component ion etch recipes to achieve the desired thin film stack patterns. Furthermore, to successfully integrate multiple film stacks into sub-micron features with the correct magnetic and signal sensitivity each layer within the device must be clean from polymer, ionic and other forms of organic/inorganic contamination or residue. Such undesired residue will adversely affect the device performance and reliability.
Traditional chemistry used in cleaning processes of thin film heads, including photoresist strip and metal lift-off, do not offer acceptable performance for modern head technology. Known photoresist removal or stripping formulations are typically contain strong alkaline solutions, organic polar solvents or strong acids and oxidizing agents. Typical organic polar solvents include pyrolidones such N-methyl pyrrolidone, N-ethyl pyrrolidone, N-hydroxyethyl pyrrolidone and N-cyclohexyl pyrrolidone; amides including dimethylacetamide or dimethylformamided; phenols and derivatives thereof. Such solvents have been used in combination with amines or other alkaline material. For example, U.S. Pat. No. 5,334,332 (Lee) discloses a composition 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-pyrrolidinone and 10 to 70% dialkyl sulfone.
Known stripping formulations are not effective in MR/GMR or spin valve head manufacture due to the corrosive nature of such formulations toward the metals used in thin film head manufacture. Thin film heads are unlike semiconductor devices and are ultra sensitive to galvanic and water induced mouse-bite corrosion, as well as, electrostatic discharge (“ESD”). For these reasons, modern thin film head back-end processes are now DI water-free and utilize isopropanol for rinse and dry steps of the cleaning sequence. This helps to minimize pole tip recession and corrosion at the thin film head level.
For example, U.S. Pat. No. 4,518,675 (Kataoka) discloses stripping compositions including dimethylsulfoxide and at least one compound selected form alkali metal alkoxides, alkali metal hydroxides and tetraalkylammonium hydroxides. Such stripping compositions are corrosive to thin films used in the manufacture of thin film heads.
In addition, known stripping compositions have numerous other drawbacks including, undesirable flammability, toxicity, volatility, odor, necessity for use at elevated temperatures such as up to 100° C., and high cost due to the handling of regulated materials.
There is thus a continuing need for strippers that effectively remove polymeric material, are more environmentally compatible and do not cause corrosion of the substrate, particularly thin metal films in the substrate.
SUMMARY OF THE INVENTION
It has been surprisingly found that polymeric material may be easily and cleanly removed from substrates, particularly thin film heads for disk drive and storage media devices. Such polymeric material may be removed according to the present invention without corrosion of underlying metal layers. Yield losses due to corrosion or erosion are also improved by using the stripping compositions of the present invention.
In one aspect, the present invention provides a composition for the removal of polymeric material from a substrate including one or more polar aprotic solvents, one or more polymer dissolution enhancing bases, and one or more corrosion inhibitors, wherein the composition is substantially free of hydroxylamine or hydroxylamine derivatives.
In a second aspect, the present invention provides a method of removing polymeric material from a substrate including the step of contacting a substrate containing polymeric material to be removed with the composition described above.
In a third aspect, the present invention provides a method for preparing thin film heads including the steps of contacting a thin film head precursor containing polymeric material to be removed with a composition including one or more polar aprotic solvents, one or more polymer dissolution enhancing bases, one or more corrosion inhibitors and one or more organic additives for a period of time sufficient to remove the polymeric material and rinsing the substrate.
DETAILED DESCRIPTION OF THE INVENTION
As used throughout this specification, the following abbreviations shall have the following meanings unless the context clearly indicates otherwise: DMSO=dimethyl sulfoxide; TMAH=tetramethylammonium hydroxide; NMP=N-methylpyrrolidone; DPM=dipropylene glycol monomethyl ether; TPM=tripropylene glycol monomethyl ether; AEEA=aminoethylaminoethanol; DI=deionized; % wt=percent by weight; mL=milliliter; ° C.=degrees Centigrade; ppb=parts per billion; and min=minute. All percents are by weight. All
Sahbari Javad J.
Sahbari Shawn J.
Cairns S. Matthew
Gupta Yogendra N.
Shipley Company L.L.C.
Webb Gregory E..
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