Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-07-17
2003-09-02
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S690000, C428S690000, C427S127000, C427S128000, C427S130000, C427S131000, C427S132000
Reexamination Certificate
active
06613459
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a master magnetic information carrier such as a master disk used in preformatted recording of servo signals, address signals or regenerative clock signals of a magnetic recording medium, in particular, relates to a master magnetic information carrier having embedded magnetic layers that records the servo signals and the like, and a fabrication method thereof. The invention also relates to a magnetic contact duplication technology in a manufacturing process of a magnetic recording medium.
BACKGROUND ART
In a hard disk drive (hereinafter referred to as HDD), for example, recording and reproduction (or writing and reading) of data are processed while a magnetic head flies over a surface of a rotating magnetic recording disk by a floating mechanism called slider holding a flying height of several tens of nm. The bit information on the magnetic recording disk is stored in concentric data tracks on the disk. Read/write of the data is conducted by quickly moving and positioning the read/write head to the target data trace Each of concentric circles on the magnetic recording disk has preformatted fields recording in a certain angular interval the preformatted information including tracking servo signal for detecting relative position between the head and the data track, address signal or generative clock signal, and the data recording and reproducing head automatically detect its own position in a certain time interval. The preformatted information is written on the magnetic recording disk using a special writing apparatus called servo track writer after the disk is installed in a HDD, so that for the center of the writing signal of the preformatted information should not be off-centered from the disk center or the center of the head orbit.
In the meantime, recording density of the magnetic recording disk has currently reached as high as 20 Gbit/in
2
in the development phase, and the recording capacity is increasing at a rate of 60% a year. Consequently, the density of the preformatted information for detecting the position of the head has necessarily increased. The prolonged time for writing the preformatted information is becoming a severe factor that lowers productivity of the HDD and raising its cost.
Recently, a preformatting recording technology has been proposed where whole of the preformatted information is transcribed at the same time in a areal manner by means of magnetic contact duplication technique utilizing a master disk, instead of linearly writing along each track utilizing a signal-writing head of the servo track writer. This technology is expected to shorten the preformatting time.
FIG.
10
(
a
) through FIG.
10
(
c
) and FIG.
11
(
a
) and FIG.
11
(
b
) illustrate the magnetic contact duplication technique. FIG.
11
(
a
) is a cross sectional view showing an initial demagnetization process where permanent magnet
2
is moved in a circumferential direction above the surface of the magnetic recording disk
1
. Since the structure of the magnetic recording disk
1
is well known, the figure simply shows a substrate
1
a
and a magnetic layer
1
b
laminated thereon. The magnetic layer
1
b
is not magnetized in one direction in the beginning, and is magnetized in the initial magnetization step uniformly in one direction, a circumferential direction, by leakage flux of the permanent magnet
2
. The arrows in the magnetic layer
1
b
represent the direction of demagnetization field A. The curved arrow in FIG.
10
(
a
) shows the moving path of the permanent magnet
2
.
Then, a master disk for magnetic contact duplication is disposed in position on the magnetic recording disk
1
to which initial demagnetization has been performed, as shown in FIG.
10
(
b
) and FIG.
1
(
b
). Embedded magnetic films
3
a
, which are Co-based soft-magnetic films, are discretely embedded in surface region of the master disk
3
, surrounded by surface portion
3
b
of the substrate.
Magnetic contact duplication is performed by moving the permanent magnet
4
on the master disk
3
, as shown in FIG.
10
(
c
) and FIG.
11
(
b
). The curved arrow in FIG.
10
(
c
) indicates the moving path of the permanent magnet
4
. The magnetic field in the duplication step is the leakage flux from the permanent magnet
4
, the direction of which is reversed from the demagnetization field A. During the movement of the permanent magnet
4
, the leakage flux pass through the surface portion
3
b
of the substrate and reach the magnetic layer
1
b
of the magnetic recording disk
1
and reverse the field direction of the demagnetization A to produce recording magnetization B with high coercive force. In the embedded magnetic film
3
a
, in contrast, the leakage flux passes along the surface direction of the magnetic film so that magnetic resistance of the magnetic path is minimized. Since the leakage flux does not reach the magnetic layer
1
b
of the magnetic recording disk
1
, the demagnetization A remains, thus a negative pattern of the pattern of the embedded magnetic film
3
a
is magnetically transferred onto the magnetic recording disk
1
. In this magnetic contact duplication technique, the magnetic recording disk is not magnetized by leakage flux of the embedded magnetic film
3
a
of the master disk
3
, but is selectively magnetized by the leakage flux from the permanent magnet
4
through the surface portion
3
b
of the substrate, while the embedded magnetic films
3
a
function as a magnetic contact duplication mask that shields parts of the leakage flux from the permanent magnet
4
.
FIG.
12
(
a
) through FIG.
12
(
e
) show a method for manufacturing a master disk
3
having embedded magnetic films
3
a.
First, photoresist of 1 &mgr;m thick is applied by spin-coating on a silicon substrate
3
c
of about 500 &mgr;m thick, followed by patterning by means of photolithography commonly used in producing silicon semiconductor devices, to form an etching mask
5
, as shown in FIG.
12
(
a
). Then, grooves
6
of depth of about 500 nm are dug by dry-etching the surface of the silicon substrate
3
c
by means of reactive plasma etching technique using reactive gas of methane trichloride, as shown in FIG.
12
(
b
). Then, Co-based soft-magnetic film
7
of about 500 nm thick is deposited by sputtering on the substrate with the mask
5
left thereon, to form an embedded Co-based soft-magnetic film
7
in the dug groove
6
, as shown in FIG.
12
(
c
). Finally, the resultant substrate
3
c
is dipped in solvent to remove the mask
5
and the Co-based magnetic film
7
thereon, remaining the Co-based soft-magnetic film
7
in the groove
6
as embedded magnetic films
3
a
. Thus, a master disk
3
with a flat surface having embedded magnetic films
3
a
is obtained.
The master disk manufactured by the above-described manner, however, involves the following problems.
FIG.
12
(
c
) shows an ideal cross sectional structure in a deposition process of Co-based soft-magnetic film
7
, where every sputtered Co particle travels to the bottom surface of the groove
6
of the substrate
3
c
with incident angle exactly perpendicular to the bottom surface and is not deposited on the inner side-wall of the groove
6
or side-wall of the mask
5
. However, because the traveling particles include obliquely incident component as well as perpendicularly incident component, deposition occurs on the inner side-wall of the groove
6
and side-wall of the mask
5
, as illustrated in FIG.
12
(
e
), which is an enlarged cross section of the portion of FIG.
12
(
c
) enclosed by two-dot chain line. Within the groove
6
, depositing speed of the incident particles is fast due to shielding effect. Consequently, in the cross-sectional configuration after removing the mask
5
with solvent there are left recesses
8
a
and protrusions
8
b
, that are burrs of the pattern edges of the soft magnetic films, as shown in FIG.
12
(
f
) which is an enlarged cross section of the portion enclosed by two-dot chain line in FIG.
12
(
d
).
These recesses
8
a
and protrusions
8
Nimura Kazuo
Otsuki Akihiro
Saito Akira
Fuji Electric & Co., Ltd.
Rossi & Associates
Thibodeau Paul
Uhlir Nikolas J
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