Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2002-03-28
2004-09-21
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06795278
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to magnetic heads and methods of manufacturing the same, and more particularly to protecting read sensors from damage due to electrostatic discharge (ESD) during the manufacture of magnetic heads.
2. Description of the Related Art
Read sensors of magnetic heads are sensitive devices which may be easily damaged during manufacturing by electrostatic discharge (ESD). During manufacturing, a plurality of magnetic heads are formed on a wafer. For each magnetic head, a read sensor is formed over a first gap layer (G
1
) which has a first shield layer (S
1
) formed beneath it. Above the read sensor is a second gap layer (G
2
) which has a second shield layer (S
2
) formed over it. The first and second gap layers and are made of an insulating material, such as alumina, whereas the first and second shield layers are made of a conductive material, such as Permalloy. Since these conductive materials are separated by the insulating materials, different electrical potentials may exist between the read sensor and shield layers. From the constant handling of the magnetic heads during manufacturing, electrostatic charge may undesirably build up and damage the read sensors. This may result in serious yield losses, especially as the sensor element becomes smaller in both film thickness and areal dimension.
One known method of preventing ESD damage to read sensors forms a temporary electrical connection between the read sensor and the first and second shields. Conventional photolithography and patterning techniques are used during head formation to form holes through the gap layers and extend sensor materials through the holes to make electrical contact with the first and the second shields. Relatively low resistances inherent to the nature and the amount of materials utilized in the connection are created. This temporary connection crosses over a contemplated air bearing surface (ABS) line of the wafer, which is eventually cut and lapped along the ABS line.
This method advantageously prevents ESD damage to read sensors during early phases of manufacturing. However, it fails to prevent ESD damage to the read sensors during later phases of manufacturing (i.e., after cutting and lapping the ABS). Since this single connection is buried within the read sensor, it is difficult if not impossible to sever it late in the manufacturing process.
Accordingly, what are needed are methods and apparatus for protecting read sensors from damage caused by ESD during manufacturing, even after the wafer is cut and lapped along the ABS.
SUMMARY OF THE INVENTION
Methods and apparatus for protecting read sensors from damage caused by electrostatic discharge (ESD) during manufacturing are described. Advantageously, two electrical connections are formed and utilized for ESD protection: one primarily for early protection of the sensors (i.e. prior to cutting and lapping the wafer to form the ABS) and the other primarily for later protection of the sensors (i.e. after cutting and lapping the wafer to form the ABS).
More particularly, a first electrical connection between a read sensor and first and second shields is created during manufacturing for each one of a plurality of magnetic heads being formed on a wafer. Each first electrical connection crosses over a contemplated air bearing surface (ABS) line of the magnetic heads. A second electrical connection is additionally created between sensor leads and the first and the second shields for each one of the plurality of magnetic heads. Each second electrical connection is exposed on an outside surface of a magnetic head. ESD protection is advantageously provided by the first and the second electrical connections until the wafer is cut and lapped along the contemplated ABS line to form the ABS, which severs each first electrical connection. Thereafter, the wafer is cut to separate the plurality of magnetic heads from each other where each head is then processed individually. During the separation and individual processing, ESD damage is advantageously prevented by each second electrical connection. Each exposed second electrical connection is eventually severed, preferably by laser-deletion, so that each magnetic head can be used as intended.
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Albrecht Thomas Robert
Fox Ciaran Avram
Hsiao Richard
Jarrett James Devereaux
Lee Edward Hin Pong
Cao Allen
Oskorep, Esq. John J.
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