Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2000-03-17
2002-12-17
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S315000, C430S311000, C430S320000, C430S329000, C216S040000
Reexamination Certificate
active
06495311
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to magnetic tape recording head devices, and more particularly to a process for fabricating magnetic poles for such heads utilizing a bilayer photoresist where the pole pieces are fabricated utilizing a metal sputtering process to form a laminated NiFeN structure.
2. Description of the Prior Art
To improve the performance characteristics of magnetic tape recording systems, new materials for forming the shields and poles of magnetic read/write heads and new manufacturing processes are continually being developed. Such magnetic head materials must be particularly wear resistant, as compared to materials for other,magnetic heads, in that physical contact between the magnetic tape and the magnetic head occurs during the read/write process. Therefore, many magnetic shield and pole forming materials utilized in manufacturing magnetic heads for hard disk drives are not suitable for use in magnetic tape head devices because the materials lack the required wear resistance properties necessary for magnetic tape heads.
A material that is suitable for use in a magnetic tape head is a high magnetic moment laminate material consisting of alternating layers of nickel iron nitride (NiFeN), and iron nitride (FeN). This laminate material can be created utilizing an RF diode sputter deposition process, such as is described in “Magnetic Properties of FeAIN Films at Elevated Temperatures” by P. Zheng, J. A. Bain, and M. H. Kryder in J. Appl. Phys. 81 (8), Apr. 15, 1997. The present invention is a magnetic head for magnetic tape systems that is composed of the NiFeN/FeN laminate material and a method for manufacturing it.
The manufacturing method of the present invention is an additive process. That is, generally, utilizing photolithographic techniques, a resist layer is formed on a substrate and holes or trenches of a desired shape are formed in the resist layer. A desired metal (or other material) layer is then deposited on top of a resist layer such that it fills the holes and trenches. Thereafter, the resist (along with the metalization layer on top of the resist) is next removed, such that the desired feature within the holes and trenches remains. This additive process is contrasted with a subtractive process which generally starts with the deposition of a metalization layer, followed by photolithographic steps which result in blocks of resist formed above areas of the metalization layer that are desired to be retained. Thereafter, the metalization layer is removed in all uncovered areas, leaving the portions of the metalization layer that are covered by the resist. The resist is then removed such that the desired metalization features remain. While the additive and subtractive processes generally described above may yield the same ultimate result, they are significantly different with regard to materials utilized, process parameters utilized and their suitability in the manufacturing of a particular device.
With regard to the NiFeN/FeN laminate metalization layers utilized in the present invention, the use of a subtractive process is generally unsuitable for manufacturing purposes because of the large quantity of NiFeN/FeN that must be removed, and particularly because the removal of the NiFeN/FeN laminate layers in a subtraction process must be accomplished utilizing a dry etching process, such as an ion beam etching process, which can result in the redeposition of removed material and significant clean up problems that result therefrom, as is well known to those skilled in the art. Wet chemical etching of the NiFeN/FeN, an alternative subtractive process, is not practical for manufacturing because the NiFeN and FeN layers etch at different rates, leaving ragged, poorly defined edges in the final patterned structure. Therefore, the present invention utilizes an additive process and, significantly, it utilizes a bilayer liftoff resist, as is generally known to those skilled in the art, which enables the removal of the NiFeN/FeN laminate utilizing a chemical solvent, thereby avoiding any redeposition problems and creating a manufacturing process that is suitable for commercial product development. Such a bilayer liftoff process is generally taught in U.S. Pat. No. 5,532,109, entitled: Azo Dyes as Adhesion Promotion Additive in Polydimethylglutarimide, issued Jul. 2, 1996 and naming as inventors Mohammad T. Krounbi, Alfred Renaldo (an inventor hereof) and Dougas Werner, and assigned to International Business Machines Corporation, the assignee hereof.
SUMMARY OF THE INVENTION
The magnetic tape recording head of the present invention is formed with magnetic poles that are comprised of a laminated NiFeN/FeN structure. The method for fabricating the magnetic poles utilizes an additive photolithographic technique including a bilayer liftoff resist. In this fabrication method magnetic pole trenches are formed in the bilayer liftoff resist such that an undercut exists in the liftoff layer. Thereafter, the NiFeN/FeN laminated structure is sputter deposited into the trench, followed by the wet chemical removal of the bilayer resist.
It is an advantage of the magnetic tape recording head of the present invention that it is fabricated with a laminated NiFeN/FeN structure.
It is another advantage of the magnetic tape recording head of the present invention that it is fabricated utilizing a bilayer photolithographic technique which reduces cleanup problems.
It is a further advantage of the fabrication method of the present invention that it utilizes photolithographic fabrication technique including a bilayer liftoff resist.
It is yet another advantage of the fabrication process of the present invention that the patterned structures of the sputter deposited NiFeN/FeN are well formed and free of distortion.
It is yet a further advantage of the fabrication process of the present invention that it utilizes an additive photoresist process including a bilayer photoresist, wherein undercuts are formed in the liftoff layer, such that clean edges of the sputter deposited NiFeN/FeN poles are formed.
These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon review of the following detailed description which makes reference to the several figures of the drawings.
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patent: 5122387 (1992-06-01), Takenaka et al.
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patent: 5264981 (1993-11-01), Campbell et al.
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Khan Mahbub R.
Nealis Jane Ellyn
Renaldo Alfred Floyd
Westwood John David
Chacko-Davis Daborah
Guillot Robert O.
Huff Mark F.
Intellectual Property Law Offices
International Business Machines - Corporation
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