Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-06-01
2003-10-07
Whitehead, Jr., Carl (Department: 2813)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06631056
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head assembly and a method of manufacturing the same. According to the invention, the thin film magnetic head assembly includes both a wafer type and a bar type. In the wafer type thin film magnetic head assembly, a substrate is a wafer and a plurality of thin film magnetic head elements are arranged in matrix on the substrate. In the bar type thin film magnetic head assembly, a substrate is formed by a bar and a plurality of thin film magnetic heads are aligned in a longitudinal direction of the bar. The bar type thin film magnetic head assembly may be obtained by cutting the wafer type thin film magnetic head assembly.
2. Description of the Related Art
In a thin film magnetic head having a reading element constituted by a magnetoresistive element such as spin valve film or ferromagnetic tunnel junction element, the magnetoresistive element and its electrode films are embedded in an insulating film made of alumina, and first and second shield films are provided on respective sides of the insulating film. In this structure, when damage or dielectric breakdown occurs in the insulating film provided between the electrode films and the first or second shield film, there might be generated large electric noise, and an electromagnetic conversion property might be degraded.
Japanese Patent Application Laid-open Publications, Kokai Hei 8-293108, Kokai Sho 61-7714 and Kokai Hei 8-167123 and U.S. Pat. No. 5,805,390 have proposed techniques for reducing the degradation of the insulating property and avoiding the dielectric breakdown.
In the Kokai Hei 8-293108, during a wafer process in which various processes are conducted without cutting or dividing a wafer, an electric connection between the electrode films and shield films is maintained, and after the wafer process, this electrical connection is cut off. However, during the wafer process, an electrical insulating property between the electrode films and the shield films could not be measured, and therefore after cutting the wafer or bar into respective thin film magnetic heads, the measurement of the insulating property. One could not know a possible degradation of insulating property or dielectric breakdown which might be generated during the wafer process. Then, a manufacturing yield is decreased, and it is necessary to measure the insulating property for individual thin film magnetic heads. It is apparent that such a checking work is very cumbersome.
In the Kokai Sho 61-7714, there is disclosed a magnetoresistive type thin film magnetic head in which upper and lower shield films are electrically connected to each other to keep these shield films equipotential, and no electrostatic charge is stored during the operation. However, in this known magnetoresistive type thin film magnetic head, insulating property of an insulating film sandwiched between the shield film and an electrode film could not be measured, and therefore manufacturing yield is low.
In the Kokai Hei 8-167123, upon manufacturing a magnetoresistive type thin film magnetic head, upper and lower shield films, electrode films and a magnetoresistive element film are connected to each other during the wafer process, and they are separated from each other after the wafer process. However, also in this known magnetoresistive type thin film magnetic head, insulating property of an insulating film between a shield film and an electrode film could not be measured, and thus sufficiently high manufacturing yield could not be attained.
Furthermore, in the U.S. Pat. No. 5,805,390, in order to protect a MR element against the dielectric breakdown during a time period from the formation of the MR element to the installation of a MR head onto a recording and reproducing device, upper and lower shield films are short-circuited during the wafer process, and after the wafer process, upper and lower shields are connected to each other via a resistor. In this known technique, a manufacturing process becomes rather complicated and manufacturing cost is increased owing to the reason that the upper and lower shields have to be short-circuited not only during the wafer process but also after the wafer process.
SUMMARY OF THE INVENTION
The present invention has for its object to provide a thin film magnetic head assembly as well as a method of manufacturing the same, in which degradation or dielectric breakage of the insulating films provided between the shield films and electrode films can be effectively prevented during the manufacturing process.
It is another object of the invention to provide a thin film magnetic head assembly as well as a method of manufacturing the same, in which an insulating property of insulating films between shield films and electrode films can be measured.
It is still another object of the invention to provide a thin film magnetic head assembly and a method of manufacturing the same, in which shield films and electrode films can be isolated without injuring the shield films.
According to the invention, a thin film magnetic head assembly includes a substrate and a plurality of thin film magnetic head elements provided on the substrate, wherein each of said thin film magnetic head element comprises:
a first shield film formed to be supported by said substrate;
a first insulating film formed on said first shield film:
a magnetoresistive element formed on the first insulating film;
first and second electrode films formed on said first insulating film to be connected to respective end portions of the magnetoresistive element;
a second insulating film formed to cover said magnetoresistive element as well as said first and second electrode films;
a second shield film formed on said second insulating film; and
a conductive film formed on said first insulating film such that the conductive film extends outside said second shield film viewed in a film stacking direction and is connected to at least one of said first and second electrode films as well as to at least one of said first and second shield films.
In the thin film magnetic head assembly according to the invention, in each of the thin film magnetic head elements, the first insulating film is formed on the first shield film and the magnetoresistive element and first and second electrode films are formed on the first insulating film, and thus the magnetoresistive element and first and second electrode films are shielded by the first shield film when the substrate is divided into respective thin film magnetic heads. Furthermore, since the first and second electrode films and magnetoresistive element are covered with the second insulating film and second insulating film is covered with the second shield film, the magnetoresistive element and first and second electrode films are shielded also by the second shield film.
Each of a plurality of the thin film magnetic head elements of the thin film magnetic head assembly according to the invention includes the conductive film. This conductive film is provided on the first insulating film to extend outside at least of the second shield film among the first and second shield films and is electrically connected to at least one of the first and second electrode films as well as to at least one of the first and second shield films. For the sake of simplicity, now a case in which the conductive film is connected to the first electrode film and second shield film will be explained. In this case, the first electrode film becomes equipotential with the second shield film, and the second electrode film becomes equipotential with the first electrode film via the second shield film, and thus the second electrode film becomes equipotential with the second shield film. Therefore, during the wafer process, no voltage is applied across the second insulating film provided between the first and second electrode films and the second shield film. In this manner, the second insulating film can be prevented from being damaged or broken due to the electrostatic charge.
When the conductive f
Asatani Takashi
Kimura Fujimi
Sato Jun-ichi
Dolan Jennifer M
Jr. Carl Whitehead
TDK Corporation
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