Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-01-30
2001-01-09
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603150, C029S603160, C029S737000, C451S005000, C451S001000
Reexamination Certificate
active
06170149
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistive head, a method of manufacturing the same, and an apparatus for manufacturing the same and, more particularly, a method of manufacturing a magnetoresistive head including a shaping step that includes polishing the magnetoresistive head, a magnetoresistive head obtained by the method, and an apparatus for manufacturing the magnetoresistive head.
2. Description of the Prior Art
A reproduction magnetic head for a high density magnetic disk apparatus has a magnetoresistive device in which electric resistance is varied according to intensity of a magnetic field. As a magnetoresistive head (referred to as a “MR head” hereinafter), there are AMR (anisotropic magnetoresistive) heads that use an anisotropic magnetoresistive effect, spin valve heads that use a spin valve effect, and the like.
In the MR head, change in resistance may be detected as change in voltage by supplying a constant current to a sense area for a signal magnetic field. It is not preferable that the sense area has too small resistance value since change in resistance caused by the signal magnetic field becomes small.
For this reason, the resistance value of the MR head has been adjusted appropriately. As one method of adjusting such resistance value, there is a method of polishing a top end of a pattern that is part of the MR head. In this case, the MR head which is formed on a rod-like block cut out from a wafer is polished.
As methods of optimizing a polishing amount of the MR head, two following methods have been adopted. These two methods are similar in that the rod-like block and the MR head are polished simultaneously with abutting the top end of the MR head formed on the rod-like block to an abrasive cloth, but different in a process of monitoring—therefor; a polishing amount.
In the first method, as shown in
FIG. 1
, on a rod-like block
101
polished with an abrasive cloth
100
, a polishing amount is measured by observing optically a height of monitoring patterns
103
which are arranged on the both sides of the MR head
102
by a microscope or the like.
However, since the monitoring patterns
103
to be measured optically, as well as the MR head
102
, are covered with a protection film (not shown), sometimes dual images of the monitoring patterns
103
are observed because of optical irregular reflection by the protection film. This causes reduction in measuring precision.
In the second method, as shown in
FIG. 2A
, on the rod-like block
101
polished with the abrasive cloth
100
, monitoring wirings
105
are first connected to conductive monitoring patterns
104
which are arranged on the both sides of the MR head
102
, and resistance values of the monitoring patterns
104
are then measured by supplying electric current to the monitoring patterns
104
.
Measurement of change in the resistance value by polishing operation may be carried out with respect to the MR head
102
. A relationship between polishing dimension of the MR head
102
and the resistance value RF and a relationship between polishing dimension of the monitoring patterns
104
and the resistance value RF have been given as curves A and B in
FIG. 2B
, for example. Therefore, polishing dimension may be calculated based on the resistance value. In other words, in principle, a desired dimension has been polished when a predetermined resistance value has been detected.
However, since there exist variation of contact resistance and error of every manufacturing step in the monitoring patterns
104
and the MR head
102
, respective rod-like blocks
101
are likely to exhibit uneven characteristic curves A and B in
FIG. 2B
even if the monitoring patterns
103
and the MR head
102
are formed to have the same structure. If the characteristic curves deviate from each other, different polishing dimensions are caused even if the same resistance value has obtained after polishing, which results in uneven characteristics of the devices.
Furthermore, in the above two polishing method, there is a disadvantage that much time and labor are required for polishing operation since the polishing is interrupted to monitor polishing states.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of manufacturing a magnetoresistive head capable of monitoring an optimum polishing location without interruption of polishing and making characteristics of the MR devices uniform after polishing, a magneto-resistive type magnetic head obtained by this method, and an apparatus for manufacturing a magnetoresistive head.
According to the present invention, a top end portion of a magnetoresistive device is polished while applying a magnetic field to the magnetoresistive device, and polishing operation is terminated at an instance when change in resistance value relative to change in the magnetic field reaches a predetermined value.
More particularly, the present invention is characterized in that an end point of polishing is not determined based on the measurement of polishing dimension of monitoring patterns or overall resistance of the MR head, but an end point of polishing is detected while measuring change in magnetic field with respect to the resistance value of the MR head. According to such monitoring method, since contact resistance of the magnetoresistive device and resistance variation derived from the monitoring process can be removed a parameters for detecting the end point of polishing, variations in remaining widths of the magnetoresistive device variations can be made small after which results in uniform device characteristics.
In addition, according to a method of polishing the magnetoresistive device making use of such monitoring, necessity of interruption is avoided to monitor polishing of the magnetoresistive device. Further, if an amount of change in resistance is set in advance to determine an end point of polishing, such end point of polishing can be easily determined so that automatic detection of the end point of polishing can be facilitated.
Furthermore, in case a plurality of magnetoresistive devices are polished simultaneously, yielding can be improved if, after variation of changes in resistance is detected, weighted distribution of polishing is reallocated so as to reduce difference in these changes in resistance. According to the above method of polishing the magnetoresistive device, the uniform MR head without variation in device characteristics can be accomplished.
Other and further objects and features of the present invention will become obvious upon an understanding of the illustrative embodiments about to be described in connection with the accompanying drawings or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employing of the invention in practice.
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Iijima Nobuo
Oshiki Mitsumasa
Watanuki Motoichi
Fujitsu Limited
Greer Burns & Crain Ltd
Tugbang A. Dexter
Young Lee
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