Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-02-15
2003-01-21
Nguyen, Hoa T. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06510022
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to thin film magnetic heads and methods for manufacturing such heads, and more particularly to the features of the P
2
pole tip/yoke interface of thin film magnetic write head elements and methods for manufacturing the P
2
pole tip/yoke interface.
2. Description of the Prior Art
The well known basic components of thin film magnetic write heads include a first pole (P
1
), a write gap layer, a narrow P
2
pole tip, a yoke that is electromagnetically engaged with the P
2
pole tip, and electromagnetic coils that generate a magnetic flux that flows between the P
1
pole and the P
2
pole tip. The width of the P
2
pole tip generally defines the track width of the data bits written by the write head. The yoke is generally significantly wider and thicker than the P
2
pole tip and it serves to control and focus the flow of magnetic flux generated by the electromagnetic coils of the write head into the P
2
pole tip. The flow of magnetic flux between the P
1
pole and the P
2
pole tip across the write gap influences the magnetic media disposed proximate the write head to record flux changes therein as data bits. Thus, a significant performance characteristic of write heads is the proper controlled flow of magnetic flux from the yoke into the P
2
pole tip and across the write gap. Where the magnetic flux flow control is faulty, the magnetic flux can flow directly from the yoke to the P
1
pole without passing through the P
2
pole tip. This undesirable effect is termed “side writing” as it creates an undesirable noise band on each side of the data track that is written by the P
2
pole tip, and the existence and width of the undesirable side band affects the spacing between the data tracks. Where side writing is minimized, such that the width of the side bands is minimized, data tracks can be written closer together such that more tracks per inch (TPI) can be written and the areal data storage of the magnetic media can be increased.
In prior art pole tips of various designs, the P
2
pole tip/yoke interface is characterized as a “T” interface. That is, the P
2
pole tip is the downward leg of the “T” and the yoke is formed flatly and squarely on top of the P
2
pole tip leg. Thus the inner angle between the P
2
pole tip and the yoke is approximately a right angle. This right angle P
2
pole tip/yoke interface results in less than optimum magnetic flux flow control between the yoke and the P
2
pole tip. That is, flow of magnetic flux is somewhat inhibited at the right angle interface, and this can result in side writing when the magnetic flux flows directly from the yoke to the P
1
pole, rather than flowing through the P
2
pole tip. It is therefore possible to improve the flow of magnetic flux through the P
2
pole tip/yoke interface and thus reduce side writing by shaping the interface to remove the right angle joinder of the yoke to the P
2
pole tip. The present invention is a write head that includes such an improved P
2
pole tip/yoke interface, together with a process for manufacturing it.
SUMMARY OF THE INVENTION
The thin film magnetic head of the present invention includes an improved P
2
pole tip/yoke interface structure. The interface structure includes yoke material that is formed in a concave curved shape at the interface between the P
2
pole tip and the yoke, such that a right angle interface between the P
2
pole tip and the yoke is eliminated.
The process for forming the P
2
pole tip/yoke interface includes a second CMP polishing step that is performed on the surface of the write head wafer subsequent to the plating of the P
2
pole tip thereon, and subsequent to a first CMP step. This second CMP step utilizes a relatively soft polishing pad and an acidic polishing slurry having a pH within the range of approximately 1 to approximately 5, and preferably approximately 2.5. The acidic polishing slurry contains a chemical agent which preferentially attacks the P
2
pole tip material, such that the second CMP step results in the recession of the upper surface of the P
2
pole tip relative to the dielectric layer surrounding it, as well as the significant rounding of the upper edges of the dielectric trench in which the P
2
pole tip is formed. Thereafter, when the yoke is plated onto the P
2
pole tip the rounded upper edges of the dielectric trench result in a concave curved interface between the yoke and the P
2
pole tip.
The resulting P
2
pole tip/yoke interface possesses improved magnetic flux flow control properties and results in decreased side writing. Greater track per inch areal data storage results from the reduced side writing of the improved write head.
It is an advantage of the magnetic head of the present invention that increased areal data storage is obtained.
It is another advantage of the magnetic head of the present invention that reduced side writing from the write head is obtained.
It is a further advantage of the magnetic head of the present invention that data tracks on magnetic media can be written closer together because the side band noise created by side writing is reduced.
It is a yet another advantage of the magnetic head of the present invention that improved magnetic flux flow control through the P
2
pole tip/yolk interface is obtained.
It is an advantage of the process for manufacturing a magnetic head of the present invention that a second CMP polishing step on the write head performed immediately following a first CMP polishing step results in a magnetic head having improved performance characteristics.
It is another advantage of the process for manufacturing a magnetic head of the present invention that a second CMP polishing step on the write head following a first CMP polishing step adds little to the manufacturing time of the write head elements.
It is a further advantage of the process for manufacturing a magnetic head of the present invention that a second CMP polishing step following a first CMP polishing step adds little to the manufacturing expense of the write head elements.
These and other features and advantages of the present invention will become better known and understood upon reading the following detailed description which makes reference to the several figures of the drawings.
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Lahiri Ashok
Lee Edward Hin Pong
Lee Eric James
Xu Hong
Guillot Robert O.
Intellectual Property Law Offices
Nguyen Hoa T.
Tianjie Chen
LandOfFree
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