Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-08-15
2003-02-18
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S492300, C204S298360, C029S603130
Reexamination Certificate
active
06521902
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to devices and methods for manufacturing magnetic recording heads, and more particularly to devices and methods for utilizing focused ion beam milling devices to trim recording head pole tips.
2. Description of the Prior Art
Thin film magnetic recording heads are generally utilized in the data storage industry to record data onto magnetic media, such as magnetic hard disks. It is an industry-wide goal to store ever increasing quantities of data upon the magnetic media by increasing the areal density of the data stored on the media. The areal density is typically increased by increasing the linear density of the data bits (bits per inch, BPI), and/or by writing the data in narrower tracks (tracks per inch, TPI). With regard to hard disks, where the data is written in narrower circular tracks on the disk, more data tracks per inch can be written and therefore more data can be stored on the disk when the TPI is increased.
The width of the data track that is written by a recording head is generally determined by the width of the second magnetic pole, termed the P
2
pole, of the write head, and efforts have been undertaken in the prior art to devise methods for reducing the width of the base of the P
2
pole, commonly referred to as the P
2
B dimension. These prior art methods have included the use of ion beams to irradiate selected areas of the P
2
pole to remove material and thereby reduce the P
2
B dimension.
With particular regard to the present invention, the use of a focused ion beam (FIB) to mill portions of the P
2
pole to reduce the P
2
B dimension is known. For instance, the Micrion MicroMill HT is a FIB tool system manufactured by the Micrion Corporation, Peabody, Mass., that is specifically designed for milling magnetic heads. Such prior art efforts have indeed reduced the P
2
B dimension, however the use of such FIB tools, particularly where the P
2
B dimension is quite small can be problematic. The problems are created during the preliminary step of accurately aligning the FIB tool to accomplish accurate beam milling in the selected portions of the P
2
pole. The accurate alignment has previously necessitated the FIB tool imaging of the entire P
2
pole in order to align the milling boxes of the FIB tool on the desired portions of the P
2
pole for material removal. The FIB tool imaging is accomplished by irradiating the imaged surface with the FIB tool ion beam such that the secondary emissions from the irradiated surface are used for visualization purposes. Significantly, the ion beam irradiation that is necessary for visualization and alignment actually performs unwanted milling on all of the irradiated surface area that is being imaged. Where the read head dimensional parameters and tolerances are small, as is the case where increased areal density of data storage is desired, the milling of critical surfaces during the P
2
pole imaging step for milling box alignment can result in seriously degraded performance of the writing components and reading components of the recording head through recession of pole tip components away from the air bearing surface (ABS) of the recording head. Therefore, a need exists for an improved method for aligning the milling pattern of an FIB tool for pole tip trimming which does not require imaging of critical pole tip components during the milling box alignment process. The present invention provides such an improved FIB tool alignment method.
SUMMARY OF THE INVENTION
The improved method for trimming a magnetic head utilizing a FIB tool includes a step of aligning the FIB tool milling boxes without imaging critical pole tip components and structure. The method includes the creation of an alignment box that is disposed in a known, fixed orientation relative to the FIB tool milling boxes. The FIB tool is aligned by imaging only the alignment box and by moving the alignment box relative to known pole tip structural characteristics that are disposed away from the critical pole tip components. The alignment box is visually aligned on non-sensitive pole tip components in such a manner that the milling boxes will be properly aligned relative to the sensitive pole tip components. FIB tool milling is thereafter performed within the milling boxes which have been accurately aligned without imaging of sensitive pole tip components.
It is an advantage of the present invention that the performance characteristics of FIB tool trimmed magnetic recording heads is improved, such that the areal density of data written on magnetic media can be increased.
It is another advantage of the present invention that more accurate writing of data to magnetic media and reading of data from magnetic media is obtained.
It is a further advantage of the present invention that critical magnetic head components are not degraded during FIB tool trimming.
It is a further advantage of the present invention that the alignment of FIB tool milling boxes upon a pole tip is achieved without ion beam irradiation of critical pole tip components.
It is yet another advantage of the present invention that electrostatic damage to critical head components is reduced, because such components are not irradiated by the ion beam.
It is yet a further advantage of the present invention that a FIB tool milling box configuration has been developed which includes an alignment box and at least one milling box, such that the milling box can be accurately aligned upon a pole tip through FIB tool imaging of only the alignment box upon top portions of the P
2
pole.
These and other objects and advantages of the present invention will become well understood by those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawings.
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patent: 5541411 (1996-07-01), Lindquist et al.
patent: 6269533 (2001-08-01), Dugas
patent: 6332962 (2001-12-01), Athas et al.
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patent: 06-134582 (1994-05-01), None
patent: 06-134583 (1994-05-01), None
patent: 07-122484 (1995-05-01), None
patent: 09-164489 (1997-06-01), None
patent: 10-092364 (1998-04-01), None
Annotated photograph illustrating use of Micrion ion milling device dated Mar. 9, 1998.
Micrion MicroMill HT, Focused Ion Beam Systems.
Journal of Applied Physics, vol. 87, No. 9, May 1, 2000, Design tradeoffs for beyond 10 Gb/in.2: Using a merged notched head on advanced low noise media (invited).
Digests of the Magnetic Recording Conference, 1998 Magnetic Recording Heads, Aug. 17-19, 1998, Boulder, Co.
IEEE Transactions on Magnetics, Mar. 1999, vol. 35, No. 2, IEMGAQ (ISSN 0018-9464).
Chang Thomas Young
Parker Michael Andrew
Fernandez Kalimah
Guillot Robert O.
Intellectual Property Law Offices
International Business Machines - Corporation
Lee John R.
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