U.S. patent application number 12/363078 was filed with the patent office on 2009-06-04 for magnetic recording medium, method of manufacturing the same, and magnetic recording/reproducing apparatus.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Yoshiyuki Kamata, Masatoshi Sakurai, Takayuki Yamamoto.
Application Number | 20090142620 12/363078 |
Document ID | / |
Family ID | 35480955 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090142620 |
Kind Code |
A1 |
Yamamoto; Takayuki ; et
al. |
June 4, 2009 |
MAGNETIC RECORDING MEDIUM, METHOD OF MANUFACTURING THE SAME, AND
MAGNETIC RECORDING/REPRODUCING APPARATUS
Abstract
A magnetic recording medium is obtained by easily patterning a
magnetic recording layer without deteriorating its electromagnetic
conversion characteristics, by forming a silicon-based protective
film between the magnetic recording layer and a photoresist, and
performing dry etching and oxygen plasma processing.
Inventors: |
Yamamoto; Takayuki;
(Ome-shi, JP) ; Sakurai; Masatoshi; (Tokyo,
JP) ; Kamata; Yoshiyuki; (Tokyo, JP) |
Correspondence
Address: |
PILLSBURY WINTHROP SHAW PITTMAN, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
35480955 |
Appl. No.: |
12/363078 |
Filed: |
January 30, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11135258 |
May 24, 2005 |
|
|
|
12363078 |
|
|
|
|
Current U.S.
Class: |
428/814 ;
430/320 |
Current CPC
Class: |
G11B 5/855 20130101;
B82Y 10/00 20130101; G11B 5/743 20130101; G11B 5/82 20130101; Y10T
428/1164 20150115; G11B 5/012 20130101; G11B 5/72 20130101; G11B
2005/0029 20130101 |
Class at
Publication: |
428/814 ;
430/320 |
International
Class: |
G11B 5/33 20060101
G11B005/33; G03F 7/20 20060101 G03F007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2004 |
JP |
2004-183933 |
Claims
1. A magnetic recording/reproduction apparatus comprising a
magnetic recording medium including stacked bodies including a
magnetic recording layer formed on the nonmagnetic substrate and a
silicon based protective layer formed on the magnetic recording
layer, and patterned into a track shape or dot shape, and a
carbon-based protective layer formed on the stacked bodies and the
nonmagnetic substrate in at least one part of a region except for
the regions where the magnetic recording layer is formed, and a
recording/reproduction head.
2. An apparatus according to claim 1, wherein the silicon-based
protective layer has a thickness of 5 to 15 .ANG..
3. An apparatus according to claim 1, wherein the silicon-based
protective layer is essentially made of amorphous nitrogen-doped
silicon.
4. An apparatus according to claim 1, wherein the carbon-based
protective layer has a thickness of 5 to 20 .ANG..
5. A magnetic recording medium manufacturing method comprising:
forming a photoresist on a silicon-based protective layer of
stacked bodies having a magnetic recording layer formed on a
nonmagnetic substrate and the silicon based protective layer formed
on the magnetic recording layer; patterning the photoresist by a
photolithography technique to form a photoresist pattern
corresponding to a track shape or dot shape; partially removing the
stacked bodies by etching by using the photoresist pattern as a
mask; removing the photoresist pattern by using oxygen plasma
processing, thereby patterning stacked bodies into a track shape or
dot shape; and forming a carbon-based protective layer on the
stacked bodies and the nonmagnetic substrate in at least one part
of a region except for the regions where the magnetic recording
layer is formed.
6. A method according to claim 5, wherein the silicon-based
protective layer has a thickness of 5 to 15 .ANG..
7. A method according to claim 5, wherein the silicon-based
protective layer is essentially made of amorphous nitrogen-doped
silicon.
8. A method according to claim 5, wherein the carbon-based
protective layer has a thickness of 5 to 20 .ANG..
9. A method according to claim 5, wherein the etching is dry
etching.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of co-pending U.S.
application Ser. No. 11/135,258, filed May 24, 2005, and for which
priority is claimed under 35 U.S.C. .sctn.121. This application is
based upon and claims the benefit of priority under 35 U.S.C.
.sctn. 119 from the prior Japanese Patent Application No.
2004-183933, filed Jun. 22, 2004, the entire contents of both
applications are incorporated herein by reference in their
entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a magnetic recording medium
for use in, e.g., a hard disk apparatus using the magnetic
recording technique and, more particularly, to a magnetic recording
medium having a magnetic recording layer so patterned that magnetic
structures such as adjacent tracks are physically separated, a
method of manufacturing the same, and a magnetic
recording/reproduction apparatus using the same.
[0004] 2. Description of the Related Art
[0005] As the capacity of a magnetic recording apparatus increases,
the track density of the apparatus also increases together with its
linear bit density.
[0006] As described in, e.g., Jpn. Pat. Appln. KOKAI Publication
No. 3-142707, a so-called patterned medium is a magnetic recording
medium having, on its surface, an array of magnetic structures
corresponding to 1 bit of recording information.
[0007] This patterned medium is attracting attention because mutual
interference between bits can be reduced and ultra-high-density
recording can be performed by forming the magnetic structures by
using materials having different magnetic properties.
[0008] The magnetic recording layer of the patterned medium is
generally patterned using the photolithography technique. For
example, after a magnetic recording layer and carbon protective
layer are formed on a substrate, a photoresist is formed by
coating, and this photoresist is exposed and developed to form a
photoresist pattern corresponding to the array of the magnetic
structures described above. This photoresist pattern is used as a
mask to etch the magnetic recording layer and carbon protective
layer. After that, the photoresist pattern is removed by using
oxygen plasma etching or the like, thereby obtaining a patterned
magnetic recording layer.
[0009] When exposed to an oxygen plasma, however, the carbon
protective layer is readily removed, and the surface of the
magnetic recording layer is oxidized. This degrades the
electromagnetic conversion characteristics of the magnetic
recording layer.
BRIEF SUMMARY OF THE INVENTION
[0010] A magnetic recording medium of the present invention
comprises a nonmagnetic substrate, a magnetic recording layer
formed on the nonmagnetic substrate and patterned into a track
shape or dot shape, and a silicon-based protective layer formed on
at least a surface of the magnetic recording layer, which is
opposite to the nonmagnetic substrate.
[0011] A magnetic recording/reproduction apparatus of the present
invention comprises a magnetic recording medium including a
nonmagnetic substrate, a magnetic recording layer formed on the
nonmagnetic substrate and patterned into a track shape or dot
shape, and a silicon-based protective layer formed on at least a
surface of the magnetic recording layer, which is opposite to the
nonmagnetic substrate, and a recording/reproduction head.
[0012] A magnetic recording medium manufacturing method of the
present invention comprises sequentially forming a magnetic
recording layer and silicon-based protective layer on a nonmagnetic
substrate, forming a photoresist on the silicon-based protective
layer, patterning the photoresist by a photolithography technique
to form a photoresist pattern corresponding to a track shape or dot
shape, partially removing the magnetic recording layer and
silicon-based protective layer by dry etching by using the
photoresist pattern as a mask, and removing the photoresist pattern
by using oxygen plasma processing, thereby patterning the magnetic
recording layer and silicon-based protective layer into a track
shape or dot shape.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0013] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention and, together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
[0014] FIG. 1 is a sectional view showing the arrangement of an
example of a magnetic recording medium according to the present
invention;
[0015] FIG. 2 is a schematic view showing the arrangement of an
example of a magnetic recording/reproduction apparatus according to
the present invention;
[0016] FIG. 3 is a sectional view for explaining a manufacturing
process of the magnetic recording medium according to the present
invention;
[0017] FIG. 4 is a sectional view for explaining a manufacturing
process of the magnetic recording medium according to the present
invention;
[0018] FIG. 5 is a sectional view for explaining a manufacturing
process of the magnetic recording medium according to the present
invention;
[0019] FIG. 6 is a sectional view for explaining a manufacturing
process of the magnetic recording medium according to the present
invention; and
[0020] FIG. 7 is a sectional view for explaining a manufacturing
process of the magnetic recording medium according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] A magnetic recording medium of the present invention is a
magnetic recording medium which includes a nonmagnetic substrate,
and a magnetic recording layer formed on the nonmagnetic substrate
and patterned into a track shape or dot shape, and which further
has a silicon-based protective layer formed on at least a surface
of the magnetic recording layer, which is opposite to the
nonmagnetic substrate.
[0022] A magnetic recording/reproduction apparatus of the present
invention is an example of an apparatus using the magnetic
recording medium described above, and has the above magnetic
recording medium and a recording/reproduction head.
[0023] A magnetic recording medium manufacturing method of the
present invention is an example of a method of manufacturing the
magnetic recording medium described above, and comprises forming a
magnetic recording layer on a nonmagnetic substrate, forming a
photoresist on the magnetic recording layer, patterning the
photoresist by a photolithography technique to form a photoresist
pattern corresponding to a track shape or dot shape, partially
removing the magnetic recording layer by dry etching by using the
photoresist pattern as a mask, and removing the photoresist pattern
by using oxygen plasma processing, thereby patterning the magnetic
recording layer into a track shape or dot shape, wherein a
silicon-based protective layer is further formed on the magnetic
recording layer before the photoresist is formed, and the
photoresist is used as a mask to partially remove the magnetic
recording layer together with the silicon-based protective layer by
dry etching.
[0024] The track-shaped or dot-shaped pattern corresponds to the
array of magnetic structures of a patterned medium. Examples of the
track-shaped pattern are a spiral shape and concentric shape. In
the magnetic recording layer thus formed into any of these
patterns, adjacent tracks or dots are physically separated. In the
magnetic recording medium of the present invention, recording
tracks, tracking servo signals, address information signals,
reproduction clock signals, and the like are written in the
magnetic recording layer thus patterned.
[0025] FIG. 1 is a sectional view showing the arrangement of an
example of the magnetic recording medium according to the present
invention.
[0026] As shown in FIG. 1, the magnetic recording medium according
to the present invention comprises a nonmagnetic substrate 1
having, e.g., a disk shape, a magnetic recording layer 2, a silicon
protective layer 3, and a carbon-based protective layer 5. The
magnetic recording layer 2 is patterned into a concentric or spiral
track shape or a dot shape. The magnetic recording layer 2 has an
upper surface which is opposite to a bottom surface in contact with
the nonmagnetic substrate, and tapered side surfaces formed between
the upper surface and bottom surface. The silicon protective layer
3 is stacked on the upper surface of the magnetic recording layer
2. The carbon-based protective layer 5 is continuously formed over
the surfaces of the stacked bodies of the magnetic recording layer
2 and silicon protective layer 3, i.e., over the side surfaces of
the magnetic recording layer 2, the surface of the silicon
protective layer 3, and the surface of the nonmagnetic substrate 1
in a region except for the regions where the magnetic recording
layer 2 is formed.
[0027] Note that this sectional view shows a portion of the section
when the disk-like magnetic recording medium is cut perpendicularly
to the two major surfaces along the radial direction of the
medium.
[0028] In the present invention, a silicon-based protective layer
is further formed between the magnetic recording layer and
photoresist during the manufacture. After dry etching, those side
surfaces of the magnetic recording layer, which are removed by
etching are exposed, but at least the upper surface of the magnetic
recording layer, which is opposite to the nonmagnetic substrate is
covered with the silicon-based protective layer. If the magnetic
recording layer is exposed to an oxygen plasma when the photoresist
is removed, the exposed side surfaces are oxidized and are rendered
nonmagnetic. If these side surfaces have magnetism and information
is written in the side surfaces, the track width becomes larger
than the actual track width, or recording magnetization becomes
unstable to cause noise. However, the side surfaces of the
patterned magnetic recording layer used in the present invention
are rendered nonmagnetic. Therefore, the track width does not
increase, and no noise is produced. On the other hand, the
silicon-based protective layer protects the upper surface, and
functions as a stopper against oxygen plasma etching. Accordingly,
this upper surface does not oxidize, and good magnetism is
maintained. In the present invention as described above, a magnetic
recording medium having a patterned magnetic recording layer is
obtained without deteriorating the electromagnetic conversion
characteristics.
[0029] Also, the silicon-based protective layer can be formed by
using an apparatus for forming the magnetic recording layer, e.g.,
a sputtering apparatus, merely by appropriately changing the
target, conditions, and the like. This obviates the need for any
special apparatus, equipment, and the like. In addition, the
silicon-based protective layer can also be formed subsequently to
the formation of the magnetic recording layer. This increases the
mass-productivity. In the present invention as described above, a
magnetic recording medium having a patterned magnetic recording
layer is readily obtained at low cost without deteriorating the
electromagnetic conversion characteristics.
[0030] To reduce the magnetic spacing, the thickness of the
silicon-based protective layer is desirably as small as possible.
However, to function as an etching stopper, this silicon-based
protective layer is a continuous film in a certain aspect of the
present invention. The silicon-based protective layer has a
thickness of 5 to 15 .ANG.. If the thickness is less than 5 .ANG.,
no uniform film is easily obtained, and this often deteriorates the
effect of the anti-oxidation film or etching stopper. If the
thickness exceeds 15 .ANG., the size of the magnetic spacing
increases, and the electromagnetic conversion characteristics often
degrade.
[0031] A carbon-based protective layer can be additionally formed
on the magnetic recording layer surface and silicon-based
protective layer surface. This carbon-based protective layer can be
formed by, e.g., sputtering or plasma CVD after the photoresist is
removed by oxygen plasma processing.
[0032] In a certain aspect of the present invention, the
carbon-based protective layer has a thickness of 5 to 20 .ANG.. If
the thickness is less than 5 .ANG., no uniform film is easily
obtained, and this often deteriorates the corrosion resistance and
durability. If the thickness exceeds 20 .ANG., the size of the
magnetic spacing increases, and the electromagnetic conversion
characteristics often degrade.
[0033] Examples of a silicon-based material used in the
silicon-based protective layer are amorphous nitrogen-doped silicon
and amorphous silicon. In one aspect of the present invention,
amorphous nitrogen-doped silicon can be used. When amorphous
nitrogen-doped silicon is used, a thin high-density film can be
formed, which increases the corrosion resistance.
[0034] The photoresist pattern can be formed by using, e.g., the
photolithography technique or in-print technique. In a certain
aspect of the present invention, the in-print technique can be
used. The in-print technique has the advantage that patterning can
be performed with high accuracy and high mass-productivity.
[0035] Also, ion milling or reactive ion etching (RIE) can be used
as dry etching.
[0036] As the nonmagnetic substrate, it is possible to use, e.g.,
an NiP-plated aluminum substrate, glass substrate, and silicon
single-crystal substrate.
[0037] As a magnetic recording method, the longitudinal magnetic
recording method and perpendicular magnetic recording method can be
used. As a longitudinal magnetic recording layer, it is possible to
use, e.g., a CoCr alloy, CoCrPtTa alloy, or CoCrTaPtB alloy.
[0038] As a perpendicular magnetic recording layer, it is possible
to use, e.g., a CoCrPt-based alloy or CoPtCrO-based alloy.
[0039] An undercoating can also be formed between the magnetic
recording layer and nonmagnetic substrate.
[0040] This undercoating can be appropriately selected in
accordance with the material, desired characteristics, and the like
of the magnetic recording layer.
[0041] As the undercoating, it is possible to use, e.g., Cr, CrW,
CrMo, NiP, NiAl, and TiCr.
[0042] When the perpendicular magnetic recording method is used, a
soft magnetic backing layer, e.g., NiFe, CoZrNb, or CoFe, can be
formed between the nonmagnetic substrate and magnetic recording
layer.
[0043] FIG. 2 is a partially exploded perspective view showing an
example of the magnetic recording/reproduction apparatus of the
present invention.
[0044] A rigid magnetic disk 121 for recording information
according to the present invention is fitted on a spindle 122 and
rotated at a predetermined rotational speed by a spindle motor (not
shown). A slider 123 mounting a recording head for accessing the
magnetic disk 121 to record information and an MR head for
reproducing information is attached to the distal end of a
suspension 124 which is a thin leaf spring. This suspension 124 is
connected to one end of an arm 125 having, e.g., a bobbin which
holds a driving coil (not shown).
[0045] A voice coil motor 126 as a kind of a linear motor is
attached to the other end of the arm 125. This voice coil motor 126
includes the driving coil (not shown) wound around the bobbin of
the arm 125, and a magnetic circuit having a permanent magnet and
counter yoke opposing each other with the driving coil sandwiched
between them.
[0046] The arm 125 is held by ball bearings (not shown) formed in
two, upper and lower portions of a fixed shaft 127, and pivoted by
the voice coil motor 126. That is, the position of the slider 123
on the magnetic disk 121 is controlled by the voice coil motor 126.
Reference numeral 128 in FIG. 2 denotes a lid.
[0047] An embodiment of the present invention will be described in
detail below.
[0048] FIGS. 3 to 7 are views for explaining the manufacturing
process of the magnetic recording medium according to the present
invention.
[0049] Referring to FIGS. 3 to 7, the patterned magnetic recording
layer side surfaces are illustrated not as tapered surfaces but as
surfaces perpendicular to the nonmagnetic substrate for the sake of
convenience.
[0050] First, as shown in FIG. 3, a glass substrate 65 mm in
diameter was used as a nonmagnetic substrate 1, and a 100-nm thick
CoZrNb soft magnetic under layer 6 and 25-nm thick CoCrPt
perpendicular magnetic recording layer 2 were formed by using DC
magnetron sputtering at an Ar gas pressure of 2 mmTorr, an input
power of 300 W, and a substrate temperature of 230.degree. C.
[0051] On the surface of the CoCrPt perpendicular magnetic
recording layer 2, a 2-nm thick amorphous silicon layer 3 was
formed in an argon ambient by DC magnetron sputtering at an argon
gas pressure of 5 mTorr and an input power of 250 W.
[0052] The amorphous silicon layer 3 was coated with a photoresist
to obtain a photoresist coating layer 7.
[0053] As shown in FIG. 4, the obtained photoresist coating layer 7
was exposed and developed by using a mask, thereby forming a
desired photoresist pattern 4.
[0054] After that, as shown in FIG. 5, the photoresist pattern 4
was used as a mask to remove unnecessary portions of the magnetic
recording layer, thereby obtaining a patterned magnetic recording
layer 2.
[0055] As shown in FIG. 6, the resist was removed by using an
oxygen plasma. More specifically, the resist was removed by using
an reactive ion etching (RIE) apparatus at an oxygen flow rate of
20 sccm, a total pressure of 30 mTorr, and an input RF power of 100
W. The end point of the etching was detected by emission analysis
by using an end point monitor.
[0056] Since the silicon layer 3 was not removed by the oxygen
plasma processing, it functioned as an ashing stop layer and also
prevented oxidation of the surface of the magnetic recording
layer.
[0057] Subsequently, as shown in FIG. 7, a 2-nm thick amorphous
hydrogen-added carbon layer 5 was formed by plasma CVD by using
methane gas as a source gas at an RF power of 200 W, a bias voltage
of -100 V, and a source gas pressure of 2 mTorr.
[0058] In addition, a 2-nm thick lubricating layer (not shown) made
of a fluorine-based liquid lubricant was formed on the carbon layer
5 by dip coating, and annealing was performed at 100.degree. C. for
30 min. Tape varnishing was performed after that, and a magnetic
disk medium was obtained through an inspection step.
[0059] When the electromagnetic conversion characteristics of the
obtained magnetic disk medium were checked, performances and
results better than those of a non-patterned magnetic recording
medium were obtained. The medium noise was also measured and found
to be low.
[0060] In the manufacturing steps of the magnetic recording medium
according to the present invention, oxidation of the magnetic layer
surface can be prevented. Therefore, the quality of recording
signals does not deteriorate. Also, the mass-productivity does not
deteriorate because the silicon-based protective layer can be
formed subsequently to the formation of the magnetic recording
layer.
[0061] When the present invention is used as described above, a
magnetic recording layer of a magnetic recording medium can be
easily patterned without deteriorating the electromagnetic
conversion characteristics of the layer. By the use of this
magnetic recording medium, therefore, low-noise,
high-recording-density recording/reproduction can be performed.
[0062] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
and scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *