Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-02-08
2003-10-14
Tugbang, A. Dexter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603070, C029S603160, C029S593000, C029S833000, C324S410000
Reexamination Certificate
active
06631547
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method for a thin film magnetic head, an inspecting method for a thin film magnetic head, and an apparatus therefor, and particularly to a manufacturing method for a thin film magnetic head, an inspecting method for a thin film magnetic head, and an apparatus therefor including an inspecting step for measuring with high accuracy dimensions of track width of a magnetic recording element in the form of a bar formed from a plurality of elements cut out of a substrate.
Recently, smaller size and larger capacity magnetic recording disk drives have been developed, and at present, small magnetic recording disk drives using a disk having the sizes of 3.5 inch and 2.5 inch have occupied the mainstream. In such a small disk drive as described above, since a rotational speed of the disk is low, where a magnetic induction type magnetic head in which a read output depends on the disk speed is used, the lowering of the read output poses a problem. On the other hand, in a magneto resistive head (hereinafter called GMR head) using a magneto resistive element (hereinafter called GMR element, GMR: Giant Magento-resistive), since the read output does not depend on the disk speed, even the small magnetic recording disk drive whose rotational speed is low is able to obtain a high read output. Further, to provide the magnetic recording disk drive having higher recording density, it is necessary to have a narrower track which narrows the track width of the magnetic head. The GMR head is advantageous in that even in case of narrower track, a high read output is obtained as compared with the magnetic induction type magnetic head. It is contemplated from the foregoing that the GMR head is a magnetic head suitable for smaller size and larger capacity.
So, there has been proposed a laminated thin film head using the GMR head as a read-back head, and a magnetic induction type magnetic head as a recording head, respectively.
On the other hand, in order to realize higher recording density, in case of face recording density of 20 G bit/inch
2
of a magnetic disk, it is necessary that track width be about 0.7 to 0.5 micro meter (&mgr;m), and in addition, with respect to the accuracy, about ±0.07 to 0.05 micro meter (&mgr;m) is required.
To exceed 60 G bit/inch
2
for higher density, it is necessary that track width be 0.3 micro meter (&mgr;m) or less, and with respect to the accuracy, about ±0.03 micro meter (&mgr;m) is expected to be required. With the narrower track as described, it is has been difficult to inspect a track width in the process of manufacturing thin film magnetic heads.
First, the manufacturing method for the GMR head which is a thin film magnetic head will be described with reference to FIGS.
2
(
a
) to (
c
). FIG.
2
(
a
) is a top view of a wafer formed with the GMR element. The GMR element is formed by a thin film process represented by sputtering, exposure, ion milling and the like, in accordance with the method not shown. In the embodiment shown in
FIG. 2
, elements are patterned by a batch exposure, as one unit U. An element formed by the thin film process is cut in the rectangular shape and separated out of a wafer
1
. FIG.
2
(
b
) shows a group of elements in the rectangular shape (hereinafter referred to as a bar
2
) separated out of the wafer. A single bar
2
is formed with a plurality of, for example, 30 GMR elements
101
(hereinafter referred to as an element
101
). FIG.
2
(
c
) shows a slider
100
having the element
101
cut out of the bar
2
. The slider
100
is incorporated into the magnetic recording disk drive by the method not shown. The typical method for forming the GMR head is described in Japanese Patent Laid-open No. Hei 8-241504.
FIG. 3
is a sectional perspective view of the GMR head. In the figure, this side of the figure is a floating surface
102
of the element
101
with respect to the disk surface (not shown). An upper magnetic shield film
103
and a lower magnetic shield film
104
perform the action for enhancing signal resolving power. A signal from a magnetic disk (not shown) close to the floating surface
102
is read by a pair of signal detecting electrodes
105
. A spacing between the signal detecting electrodes
105
is a read track
106
, whose width is a read track width T
WR
. A write coil
107
is formed on the upper magnetic shield film
10
, and a write head
108
is formed above the write coil
107
. An extreme end of the write head
108
is a write track
109
whose width is a write track width T
WW
. These track widths are observed from the floating surface
102
(the arrow in the figure).
FIGS.
4
(
a
) to
4
(
c
) show the detail of the bar
2
after cut. FIG.
4
(
a
) is a view as viewed form the side for carrying out element forming by the film process, that is, from the upper surface, and FIG.
4
(
b
) is a view as viewed from the arrow of FIG.
4
(
a
), that is, from the floating surface side. Various dimensions of the element
101
are measured from this direction. In FIG.
4
(
b
), X-direction is the direction in which the elements
10
are continuously arranged, and Y-direction is the direction at right angle thereto. As described above, the bar
2
is in the rectangular shape; for example, in case of length: 50 mm, height: 15 mm, and thickness: 0.5 mm, the bar
2
is, generally, flexed like a bow as shown in FIG.
4
(
b
) although different depending on the conditions at the time of cutting, and the flexing amount S thereof is often scores of micro meters (&mgr;m) in the central part.
FIG. 5
shows the procedure for measuring in accordance with the conventional measuring method. First, the bar
2
is set to observation means such as a microscope in a direction (the floating surface side) of FIG.
4
(
b
) to observe the element
101
. First, an image of a first element is obtained, and various element dimensions of the element
101
are computed. In case of not a final element, the bar
2
is moved by 1 pitch in the direction X to obtain an image of a next element. Where an element can be measured, element dimensions are computed. This operation is repeated to find all the element dimensions. However, since the bar
2
is flexed like a bow, it is sometimes that the element is not within the detecting range when an image is obtained merely by movement in the direction X, making it impossible to measure the element dimensions. In this case, it is necessary that to enable measurement of the element dimensions, the element is moved in a direction in which the bar
2
is flexed, that is, in the direction Y so that the element is within the detecting screen. Further, where a nanometer order is detected, an aberration of an optical system need also be taken into consideration. To this end, it is necessary accurately locate an element in the center of a field of view of an objective lens for which an optical aberration is best corrected.
This will be explained in more detail with reference to FIGS.
6
(
a
) to (
c
). FIG.
6
(
a
) is an image in which a first element is detected. Since it is necessary for detecting of element dimensions with high accuracy to detect the element
10
in an enlarged scale, a field of detecting of an image is about 20 micro meters (&mgr;m). The height of the element
101
is approximately 10 micro meters (&mgr;m). For example, the bar
2
is set in the direction Y so as to assume a height Y
1
position within the measuring range
111
. The bar
2
is stepwise moved in the direction X in order to detect next element as previously mentioned. FIG.
6
(
b
) shows an image of an element in the vicinity of the center. Within the measuring range
111
, the element
101
is detected downward due to the flexure of the bar
2
to assume a height Y
2
. Since in this state, the element
101
is not within the detecting range
111
, it is impossible to measure element dimensions. Therefore, the bar
2
is moved in the direction Y, and moved so that the element
101
assumes a height Y
3
within the measuring range
111
, a
Nakata Toshihiko
Sasazawa Hideaki
Yamasaka Minoru
Yoshida Minoru
Kim Paul D
Mattingly Stanger & Malur, P.C.
Tugbang A. Dexter
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