U.S. patent application number 10/306182 was filed with the patent office on 2005-02-17 for magnetic discrete track recording disk.
Invention is credited to Bajorek, Christopher H., Bertero, Gerardo A., Chao, James L., Homola, Andrew, Treves, David, Wachenschwanz, David E..
Application Number | 20050036223 10/306182 |
Document ID | / |
Family ID | 32392465 |
Filed Date | 2005-02-17 |
United States Patent
Application |
20050036223 |
Kind Code |
A1 |
Wachenschwanz, David E. ; et
al. |
February 17, 2005 |
Magnetic discrete track recording disk
Abstract
A method of forming a discrete track recording pattern in a
magnetic recording disk. In one embodiment, the discrete track
recording pattern may be formed in a NiP layer continuous
throughout the discrete track recording pattern. Alternatively, the
discrete track recording pattern may be formed in a substrate.
Inventors: |
Wachenschwanz, David E.;
(Saratoga, CA) ; Bertero, Gerardo A.; (Redwood
City, CA) ; Treves, David; (Palo Alto, CA) ;
Homola, Andrew; (Morgan Hill, CA) ; Chao, James
L.; (Fremont, CA) ; Bajorek, Christopher H.;
(Los Gatos, CA) |
Correspondence
Address: |
Daniel E. Ovanezian
BLAKELY, SOKOLOFF, TAYLOR & ZAFMAN LLP
Seventh Floor
12400 Wilshire Boulevard
Los Angeles
CA
90025-1026
US
|
Family ID: |
32392465 |
Appl. No.: |
10/306182 |
Filed: |
November 27, 2002 |
Current U.S.
Class: |
360/48 ; 360/135;
G9B/5.299; G9B/5.306 |
Current CPC
Class: |
Y10T 29/49021 20150115;
G11B 5/667 20130101; G11B 5/855 20130101; Y10T 29/49025 20150115;
G11B 5/858 20130101; G11B 5/8404 20130101 |
Class at
Publication: |
360/048 ;
360/135 |
International
Class: |
B44C 001/22; G11B
005/09; G11B 005/82; G11B 005/72 |
Claims
1. (Canceled)
2. The method of claim 5, wherein forming further comprises a
subtractive process.
3. A method of fabricating a magnetic recording disk, comprising:
forming a discrete track recording pattern on a substrate, wherein
forming comprises: coating the substrate with an embossable layer;
and imprinting the embossable layer with the discrete track
recording pattern; and disposing a magnetic recording layer above
the substrate.
4. The method of claim 3, wherein imprinting comprises imprint
lithography.
5. The method of claim 4, wherein forming further comprises etching
the embossable layer down to the substrate to form a first
plurality of raised zones and recessed zones.
6. The method of claim 2, wherein the subtractive process comprises
etching into the substrate to form a second plurality of raised
zones and recessed zones in the substrate that forms the discrete
track recording pattern.
7. The method of claim 6, wherein forming further comprises
removing the embossable layer.
8. The method of claim 7, wherein forming further comprises
polishing the substrate after removing the embossable layer.
9. The method of claim 7, wherein forming further comprises
texturing the substrate after removing the embossable layer.
10. The method of claim 3, wherein forming further comprises
polishing the substrate before coating the substrate with the
embossable layer.
11. The method of claim 3, wherein forming further comprises
texturing the substrate before coating the substrate with the
embossable layer.
12. The method of claim 7, wherein forming further comprises
depositing a soft magnetic underlayer material over the second
plurality of raised zones and recessed zones in the substrate.
13. The method of claim 5, wherein forming further comprises an
additive process.
14-16. (Canceled)
17. The method of claim 13, wherein the additive process comprises
depositing the first plurality of recessed zones with a substrate
material to form a second plurality of raised and recessed zones in
the substrate that forms the discrete track recording pattern.
18. The method of claim 17, wherein depositing further comprises
electroplating.
19. The method of claim 17, wherein depositing further comprises
electroless plating.
20. The method of claim 17, wherein forming further comprises
removing the embossable layer.
21. The method of claim 20, wherein forming further comprises
polishing the substrate.
22. The method of claim 21, wherein forming further comprises
texturing the substrate.
23. The method of claim 20, wherein forming further comprises
depositing a soft magnetic underlayer material over the second
plurality of raised zones and recessed zones in the substrate.
24. The method of claim 13, wherein the additive process comprises
depositing a substrate material on the first plurality of raised
and recessed zones by vacuum deposition.
25. The method of claim 12, wherein forming further comprises
polishing a surface of the soft magnetic underlayer material.
26. The method of claim 12, wherein forming further comprises
texturing a surface of the soft magnetic underlayer material.
27-40. (Cancelled).
41. A method of fabricating a magnetic recording disk, the method
comprising: disposing a nickel-phosphorous (NiP) layer on a
substrate; and forming a discrete track recording pattern on the
NiP layer, wherein the NiP layer is continuous throughout the
discrete track recording pattern.
42. The method of claim 41, wherein forming comprises a subtractive
process.
43. The method of claim 42, wherein forming further comprises:
coating the NiP layer with an embossable layer; and imprinting the
embossable layer with the discrete track recording pattern.
44. The method of claim 43, wherein imprinting comprises imprint
lithography.
45. The method of claim 44, wherein forming further comprises
etching the embossable layer down to the NiP layer to form a first
plurality of raised zones and recessed zones.
46. The method of claim 45, wherein forming further comprises
etching into the NiP layer to form a second plurality of raised
zones and recessed zones in the NiP layer that forms the discrete
track recording pattern.
47. The method of claim 45, wherein forming further comprises
removing the embossable layer.
48. The method of claim 47, wherein forming further comprises
polishing the NiP layer after removing the embossable layer.
49. The method of claim 47, wherein forming further comprises
texturing the NiP layer after removing the embossable layer.
50. The method of claim 47, wherein forming further comprises
depositing a soft magnetic underlayer material over the second
plurality of raised zones and recessed zones in the NiP layer.
51. The method of claim 50, wherein forming further comprises
polishing a surface of the soft magnetic underlayer.
52. The method of claim 50, wherein forming further comprises
texturing a surface of the soft magnetic underlayer.
53. The method of claim 50, wherein forming further comprises
disposing a second NiP layer on the soft magnetic underlayer.
54. The method of claim 53, wherein forming further comprises
polishing a surface of the second NiP layer.
55. The method of claim 53, wherein forming further comprises
texturing a surface of the second NiP layer.
56. The method of claim 43, wherein forming further comprises
texturing the NiP layer before coating the NiP layer with the
embossable layer.
57. The method of claim 41, wherein forming comprises an additive
process.
58. The method of claim 57, wherein forming further comprises:
coating the NiP layer with an embossable layer; and imprinting the
embossable layer with the discrete track recording pattern.
59. The method of claim 58, wherein imprinting comprises imprint
lithography.
60. The method of claim 59, wherein forming further comprises
etching the embossable layer down to the NiP layer to form a first
plurality of raised zones and recessed zones.
61. The method of claim 60, wherein forming further comprises
depositing the first plurality of recessed zones with NiP to form a
second plurality of raised and recessed zones in the NiP layer that
forms the discrete track recording pattern.
62. The method of claim 61, wherein depositing further comprises
electroplating.
63. The method of claim 61, wherein depositing further comprises
electroless plating.
64. The method of claim 61, wherein forming further comprises
removing the embossable layer.
65. The method of claim 64, wherein forming further comprises
polishing the NiP layer.
66. The method of claim 64, wherein forming further comprises
texturing the NiP layer.
67. The method of claim 60, further comprising depositing NiP on
the first plurality of raised and recessed zones by vacuum
deposition.
68-110. (Cancelled).
Description
TECHNICAL FIELD
[0001] Embodiments of this invention relate to the field of disk
drives and, more specifically, to disks used in disk drive
systems.
BACKGROUND
[0002] A disk drive system includes one or more magnetic recording
disks and control mechanisms for storing data on the disks. The
disks are constructed of a substrate, that may be textured, and
multiple film layers. In most systems, an aluminum-based substrate
is used. However, alternative substrate materials such as glass
have various performance benefits such that it may be desirable to
use a glass substrate. One of the film layers on a disk is a
magnetic layer used to store data. The reading and writing of data
is accomplished by flying a read-write head over the disk to alter
the properties of the disk's magnetic layer. The read-write head is
typically a part of or affixed to a larger body that flies over the
disk, referred to as a slider.
[0003] The trend in the design of magnetic hard disk drives is to
increase the recording density of a disk drive system. Recording
density is a measure of the amount of data that may be stored in a
given area of a disk. To increase recording density, for example,
head technology has migrated from ferrite heads to film heads and
later to magneto-resistive (MR) heads and giant magneto-resistive
(GMR) heads.
[0004] Achieving higher areal density (i.e., the number of stored
bits per unit surface area) requires that the data tracks be close
to each other. Also, because the track widths are very small, any
misregistration of a track (e.g., thermal expansion) may affect the
writing and/or reading with the head by an adjacent track. This
behavior is commonly referred to as adjacent track interference
(ATI). One method for addressing ATI is to pattern the surface of
the disk to form discrete data tracks, referred to as discrete
track recording (DTR). DTR disks typically have a series of
concentric raised zones (also known as hills, lands, elevations,
etc.) for storing data and recessed zones (also known as troughs,
valleys, grooves, etc.) that provide inter-track isolation to
reduce noise. By putting voids between tracks, reading and/or
writing by a head may be accomplished more easily. Such recessed
zones may also store servo information. The recessed zones separate
the raised zones from one another to inhibit or prevent the
unintended storage of data in the recessed zones.
[0005] One problem with prior DTR magnetic recording disks is that
they may not have a desired "preferred" circumferential orientation
of magnetic material in their magnetic recording films. "Preferred"
circumferential orientation of the magnetic media aids in achieving
optimal signal-to-noise ratio (SNR) and resolution to obtain the
best possible performance from the magnetic media.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The present invention is illustrated by way of example, and
not limitation, in the figures of the accompanying drawings in
which:
[0007] FIG. 1A illustrates a cross-sectional perspective view of
one embodiment of a patterned disk and a write element of a
head.
[0008] FIG. 1B illustrates a cross-sectional perspective view of an
alternative embodiment of a patterned disk.
[0009] FIGS. 2A-2G show expanded cross sectional views illustrating
an exemplary embodiment of a method of forming a discrete track
recording pattern on a nickel-phosphorous layer.
[0010] FIGS. 3A-3F show expanded cross sectional views illustrating
another exemplary embodiment of a method of forming a discrete
track recording pattern on a nickel-phosphorous layer.
[0011] FIGS. 4A-4G show expanded cross sectional views illustrating
an exemplary embodiment of a method of forming a discrete track
recording pattern on a substrate.
[0012] FIGS. 5A-5F show expanded cross sectional views illustrating
another exemplary embodiment of a method of forming a discrete
track recording pattern on a substrate.
[0013] FIG. 6 is a cross section illustrating one embodiment of a
recording disk having a patterned nickel-phosphorous layer.
[0014] FIG. 7 is a cross section illustrating one embodiment of a
recording disk having a patterned substrate.
[0015] FIGS. 8A-8B show expanded cross sectional views illustrating
an exemplary embodiment of a method of depositing a soft magnetic
underlayer on a patterned substrate.
[0016] FIG. 9 is a cross section illustrating one embodiment of a
recording disk having a soft magnetic underlayer deposited on a
patterned substrate.
[0017] FIG. 10 illustrates one embodiment of a disk drive.
DETAILED DESCRIPTION
[0018] In the following description, numerous specific details are
set forth such as examples of specific materials or components in
order to provide a thorough understanding of the present invention.
It will be apparent, however, to one skilled in the art that these
specific details need not be employed to practice the invention. In
other instances, well known components or methods have not been
described in detail in order to avoid unnecessarily obscuring the
present invention.
[0019] The terms "above," "below," and "between" as used herein
refer to a relative position of one layer with respect to other
layers. As such, one layer deposited or disposed above or below
another layer may be directly in contact with the other layer or
may have one or more intervening layers. Moreover, one layer
deposited or disposed between layers may be directly in contact
with the layers or may have one or more intervening layers.
[0020] It should be noted that the apparatus and methods discussed
herein may be used with various types of disks. In one embodiment,
for example, the apparatus and methods discussed herein may be used
with a magnetic recording disk. Alternatively, the apparatus and
methods discussed herein may be used with other types of digital
recording disks, for example, optical recording disks such as a
compact disc (CD) and a digital-versatile-disk (DVD).
[0021] In one embodiment, a longitudinal magnetic recording disk
having a nickel-phosphorous (NiP) underlayer with a discrete track
recording pattern is described. The discrete track recording
pattern provides inter-track isolation within the NiP layer. The
recording disk has a substrate, a NiP layer disposed above the
substrate and a magnetic recording layer disposed above the NiP
layer. In another embodiment, methods for patterning a NiP layer
with a discrete track recording pattern are described. The NiP
layer, continuous throughout the discrete track recording pattern,
may initially be imprinted with a stamper that forms an
intermediate pattern relative the final discrete track recording
pattern. In an alternative embodiment, a method of forming the
discrete track recording pattern involves etching (e.g., plasma,
e-beam, chemical) the NiP layer in which portions of the NiP layer
are removed to form the raised and recessed zones (e.g., data and
non-data zones of a DTR pattern). In another embodiment, an
additive process may be used in which a material compatible with
the NiP layer may be plated up on the NiP layer to form the
discrete track recording pattern. In one embodiment, the discrete
track recording pattern does not extend down into the disk
substrate.
[0022] In an alternative embodiment, a discrete track recording
pattern is formed in the substrate. The patterned substrate may be
formed analogous to the subtractive or additive process for
patterning the NiP layer.
[0023] Although a discussion of the operation of a disk drive
system is not strictly necessary for the present invention, a
description thereof may aid in understanding the operation and
advantages provided by a disk having a discrete track recording
pattern. FIG. 1A illustrates a cross-sectional perspective view of
a patterned disk and a write element of a head. The disk 100
includes multiple film layers that have been omitted for clarity of
the following discussion. During operation of a disk drive, reading
and writing of data on the disk 100 is accomplished by flying, for
example, a read-write head 110 over the disk 100 to alter the
properties of the disk's magnetic layer 150. To perform a transfer
of data with the disk 100, the head 110 is centered above a track
of the rotating disk 100. The recording head 110 may be, for
example, a dual element head having a read element for performing a
read operation and a write element for performing a write
operation.
[0024] The disk 100 includes a substrate 120 that may be textured,
and multiple film layers disposed above the substrate 120. The
disks described herein may be manufactured with, by example, a
glass substrate or a metal/metal alloy substrate. Glass substrates
that may be used include, for example, a silica containing glass
such as borosilicate glass and aluminosilicate glass. Metal alloy
substrates that may be used include, for example,
aluminum-magnesium (AlMg) substrates. In an alternative embodiment,
other substrate materials including polymers and ceramics may be
used.
[0025] The multiple film layers include a NiP layer 130 and
magnetic layer 150. A discrete track recording pattern is formed
into the NiP layer 130 as discussed further below. A magnetic layer
150 is disposed above the NiP layer 130. The DTR pattern includes
recessed zones 160 and raised zones 170. The recessed zones 160
have a depth 165 relative to the recording head 110 and/or raised
zones 170. In one embodiment, the width 115 of the head 110 is
greater than the width 175 of the raised zones 170 such that
portions of the head 110 extend over the recessed zones 160 during
operation. However, the recessed zones 160 are sufficiently
separated by a distance 165 from the head 110 to inhibit storage of
data by the head 110 in the magnetic layer 150 directly below the
recessed zones 160. The raised zones 170 are sufficiently close to
the head 110 to enable the writing of data in the magnetic layer
150 directly below the raised zones 170. In one embodiment, for
example, a width 175 of each raised zone may be about 1250
angstroms (.ANG.) and a width of each recessed zone may be
typically about 1/3 of the raised zone, or about 400 .ANG.. A depth
165 of each recessed zone, for example, may be about 400 .ANG.. In
other embodiments, the raised and recessed zones may have a pitch
between about 200-2000 .ANG.. Dimensions discussed above are
exemplary and may have other values.
[0026] Therefore, when data are written to the recoding medium, the
raised zones 170 of NiP layer 130 correspond to the data tracks.
Information, such as servo (head positioning) information may be
stored in the recessed zones 160. Alternatively, servo information
may be interleaved with data in sectors on stored on the raised
zones 170. The raised zones 170 and recessed zones 160 are
typically formed as alternating concentric circles although other
configurations (e.g., spiral) are contemplated. The recessed zones
160 isolate the raised zones 170 (e.g., the data tracks) from one
another, resulting in data tracks that are defined both physically
and magnetically.
[0027] When data are written by the head 110 to a particular data
track (raised area or zone), data are inhibited from being to
adjacent recessed zones 160 because the magnetic layer 150, below
the recessed surface zone 160, is too far from the head 110 for the
head 110 to induce magnetic transitions there. If new data are
written on a subsequent write operation, there should be no
residual data from an earlier operation in the raised zones 170 or
recessed zones 160. Thus, when the head 110 reads data from a
raised zone 170, only data from the preceding write operation is
present and read.
[0028] It should be noted that various types of discrete track
patterns may be generated by stampers in addition to what is
illustrated in FIG. 1A. For example, in an alternative embodiment,
the discrete track pattern formed in the NiP layer 130 may include
data islands as illustrated in FIG. 1B. Each of the data islands
190 may hold a block of data (e.g., one bit or multiple bits) and
are isolated form one another by the recessed zones. Such a
configuration may reduce the amount of noise (e.g., noise between
tracks and between blocks of data or bits) that is sensed by the
read head 110. In other examples, the recessed and raised zones may
have alternate shapes that still isolate data blocks from recessed
zones.
[0029] A method to form a continuous NiP layer with a discrete
track recording pattern is described. The method may involve first
imprinting an embossable layer disposed above the NiP layer
followed by a subtractive or additive process to form the desired
pattern. Imprinting the embossable layer may utilize lithography
techniques, for example, nanoimprint lithography.
[0030] FIGS. 2A-2G show expanded cross sectional views illustrating
one embodiment of forming a discrete track recording pattern on a
NiP layer of a longitudinal magnetic recording disk. In this
embodiment, the method involves a subtractive process in which a
layer or layers disposed on a disk substrate may be removed (e.g.,
through imprint lithography and etching) to expose a desired
pattern on the NiP layer. For clarity of explanation, the various
layers illustrated in FIGS. 2A-2G are exemplary and may not be
scaled to representative sizes. As shown in FIG. 2A, the patterning
process begins with a disk-shaped substrate 205. Disk substrate
205, as discussed above, may be made of a number of materials
including metals (e.g., aluminum), glass, silicon or other
conventional disk substrate materials known in the art. In one
embodiment, substrate 205 may be plated with a NiP layer 215. NiP
layer 215 may be formed by electroplating, electroless plating, or
by other methods known in the art. Plating disk substrate 205 with
a rigid or metallic material such as NiP provides mechanical
support to disk substrate 205 for subsequent texturing, polishing,
and/or patterning processes. Plating of disk substrate 205 may not
be necessary, however, if disk substrate 205 is composed of a
sufficiently rigid or hard material such as glass.
[0031] The NiP plated disk substrate 205 surface may then be
polished, planarized, and/or textured as illustrated by FIG. 2B. In
one embodiment, NiP layer 215 may be polished, for example, by a
uniform etch. In alternative embodiments, other polishing
techniques may be used. Polishing techniques are well known in the
art; accordingly, a detailed discussion is not provided.
Alternatively, NiP layer 215 may not be polished. Next, in one
embodiment, NiP layer 215 may be anisotropically textured with a
pattern (e.g., cross-hatch, circumferential), by various methods
such as mechanical texturing using fixed or free abrasive particles
(e.g., diamond). Alternatively, other types of texturing methods,
such as laser texturing, may be used. Certain types of texturing,
on the intended data zones of a disk, before deposition of
nucleation and magnetic layer may encourage preferred
circumferential orientation of the magnetic media on a disk.
Preferred circumferential orientation of the magnetic media on a
disk aids in achieving optimal signal-to-noise (SNR) and resolution
to obtain the best possible performance from the magnetic media.
Alternatively, as discussed below, texturing of NiP layer 215 may
be performed after the discrete track recording pattern has been
formed.
[0032] Next, as illustrated by FIG. 2C, disk substrate 205 may then
be coated with an embossable layer 220, for example, a photoresist,
an electron sensitive resist, or other embossable materials. Spin
coating, dip coating, and spray coating are just some methods of
disposing embossable layer 220 on NiP layer 215. Other coating
methods such as sputtering and vacuum deposition (e.g., CVD) may be
used. Other embossable layer materials such as dye polymer may be
used for other examples, thermoplastics (e.g., amorphous,
semi-crystalline, crystalline), thermosetting (e.g., epoxies,
phenolics, polysiloxanes, ormosils, sol-gel) and radiation curable
(e.g., UV curable, electron-beam curable) polymers. In one
embodiment, for example, embossable layer 220 may have a thickness
in the range of about 100-5000 .ANG.. Embossable layer 220 may also
be referred to as a "masking layer" and a "stencil layer."
[0033] Next, as illustrated by FIG. 2D, embossable layer 220 is
imprinted with a pattern of recessed (222, 224, 226) and raised
(221, 223, 225) zones. The stamping of embossable layer 220 may
utilize, for example, nanoimprint lithography techniques that are
well known in the art. In one embodiment, a stamper (not shown)
bearing a discrete track recording pattern, may be used to imprint
embossable layer 220 to form recessed zones (222, 224, 226) and
raised zones (221, 223, 225). Because of the thickness of the
embossable layer 220, the imprint of raised and recessed zones are
not likely to press into NiP layer 215. Alternatively, if
embossable layer 220 is relatively thin, it may be stamped to leave
very little embossable material in the recessed zones (222, 224,
226). Subsequently, embossable material in the recessed zones (222,
224, 226) may be removed to expose NiP layer 215. The stamper used
to pattern the embossable layer 220 has the inverse, or negative
replica, of the desired pattern (i.e., the discrete track recording
pattern on NiP layer 215) to be formed.
[0034] Next, as illustrated by FIG. 2E, the intermediate pattern in
embossable layer 220 may be etched to further define the
alternating recessed zones (222, 224, 226) and raised zones (221,
223, 225) that form the basis for the discrete track recording
pattern on NiP layer 215. In one embodiment, a series, or step-wise
process of etching procedures may be performed on embossable layer
220 and NiP layer 215 to form the desired track pattern. Embossable
layer 220 serves as a stencil that exposes the NiP layer 215 in
areas beneath the recessed zones (222, 224, 226) of the pattern
formed by the stamper. In one embodiment, plasma etching is
utilized to remove embossable layer 220 material in recessed zones
(222, 224, 226) down to the NiP layer 215. Alternatively, other
etching methods may be used to remove embossable layer 220 material
in at least the recessed zones, for example, using chemical
etching, electron beam (e-beam) etching, ion-beam etching (passive
or reactive) sputter etching, and plasma etching with reactive
gases. For certain types of etching (e.g., chemical), embossable
layer material may be removed from both the raised zones (221, 223,
225) and recessed zones (222, 224, 226) at approximately a similar
rate. Chemical etching will remove the embossable layer 220 in both
the recessed zones (222, 224, 226) and raised zones (221, 223, 225)
until NiP layer 215 is exposed in the recessed zones (222, 224,
226), as illustrated by FIG. 2E.
[0035] Next, as illustrated by FIG. 2F, recessed zones (222, 224,
226) of NiP layer 215 may be further etched (e.g., by chemical,
e-beam, ion-beam, and sputter etching). In one embodiment, the
etching of recessed zones (222, 224, 226) may not penetrate through
NiP layer 215 to the disk substrate 205 such that NiP layer 215
forms a continuous pattern of recessed zones (222, 224, 226) and
raised zones (221, 223, 225). Having achieved a desired recess
depth 216, the remaining embossable layer 220 on the raised zones
(221, 223, 225) of the discrete track recording pattern may then be
removed, for example, by the methods discussed above in relation to
FIG. 2E, or by other methods such as polishing (e.g., fine, kiss,
or coarse polishing). The removal of embossable layer 220 exposes
the entire top surface of the patterned NiP layer 215, as
illustrated by FIG. 2G.
[0036] It is noted that the raised zones (221, 223, 225),
corresponding to the data recording zones of the magnetic disk may
be textured, rather than texturing the entire NiP layer 215 prior
to coating with embossable layer 220 as discussed above in relation
to FIG. 2B. Any of the texturing methods described above may be
used (e.g., mechanical and laser texturing). As discussed above,
NiP layer 215 may be textured earlier before any imprinting or
etching (e.g., as described with respect to FIG. 2B, after NiP
plating of disk substrate 205). It should also be noted that
various cleaning and/or polishing operations may be performed
between the stages discussed above. For example, one or more
polishing operations (e.g., fine/kiss, coarse) may be performed to
remove asperities from the surface of one or more of the layers.
Asperities residing on the surface of any layer may have negative
effects on the performance of the manufactured disk. With NiP layer
215 now patterned and textured with a discrete track recording
pattern, other layers (e.g., a magnetic layer, lamination layer)
may be disposed above NiP layer 215 to complete the disk
manufacturing process.
[0037] FIGS. 3A-3F show expanded cross sectional views illustrating
an alternative embodiment of forming a discrete track recording
pattern on a NiP layer of a longitudinal magnetic recording disk.
This method involves an additive process in which a material
compatible or identical to material forming the initial NiP layer
is added or plated to form the raised zones of the discrete track
recording pattern. The various layers illustrated in FIGS. 3A-3F
are exemplary and not scaled to proper sizes so that the process of
patterning the NiP layer may be described with clarity.
[0038] The additive process illustrated by FIGS. 3A-3F are
analogous to the subtractive process illustrated by FIGS. 2A-2G
with respect to the stamping and etching of the embossable layer
320 disposed above NiP layer 315. As illustrated by FIG. 3A, the
process begins with NiP layer 315 disposed on disk substrate 305
(e.g., by electro plating and electroless plating). Unlike the
subtractive process described above, the NiP plated disk substrate
305 is not necessarily textured at this point. As will be apparent
below, this method requires texturing of the final raised zones of
NiP layer 315 after the discrete track recording pattern is formed.
Disk substrate 305, may be composed of materials similar to those
discussed above with respect to the substrate 205.
[0039] As illustrated by FIG. 3B, disk substrate 305 may then be
coated with an embossable layer 320, for example, a photoresist, an
electron sensitive resist, or other embossable materials. Spin
coating, dip coating, and spray coating are just some methods of
disposing the embossable layer 320 on substrate 305. Other coating
methods (e.g., sputtering) and embossable layer materials (e.g.,
dye polymer) may be used for example, thermoplastics (e.g.,
amorphous, semi-crystalline, crystalline), thermosetting (e.g.,
epoxies, phenolics, polysiloxanes, ormosils, sol-gel) and radiation
curable polymers (e.g., UV curable, electron-beam curable).
[0040] Next, as illustrated by FIG. 3C, a stamper (not shown)
bearing a discrete track recording pattern, may be used to impress
embossable layer 320 to form recessed zones (322, 324, 326) and
raised zones (321, 323, 325). If the embossable layer 320 is thick
relative to the depth of the pattern in the stamper, the imprint
from the stamper is not likely to register deep enough to reach NiP
layer 315. Alternatively, if embossable layer 320 is relatively
thin, it may be stamped to leave very little embossable material in
the recessed zones (322, 324, 326). Subsequently, embossable
material in the recessed zones (322, 324, 326) may be removed to
expose NiP layer 315. The stamper used to pattern the embossable
layer 320 may have a pattern identical to the pattern to be formed
on NiP layer 315.
[0041] Next, as illustrated by FIG. 3D, embossable layer material
in the recessed zones (322, 324, 326) may be removed by a number of
etching methods (e.g., by chemical, plasma, e-beam, ion-beam, or
sputter etching), such that surface areas of NiP layer 315 are
exposed. For certain types of etching (e.g., chemical), embossable
layer material may be removed from both the raised zones (321, 323,
325) and recessed zones (322, 324, 326) at approximately a similar
rate. Chemical etching will remove the embossable layer 320 in both
the recessed zones (322, 324, 326) and raised zones (321, 323, 325)
until NiP layer 315 is exposed in the recessed zones (322, 324,
326), as illustrated by FIG. 3D.
[0042] Next, as illustrated by FIG. 3E, recessed zones (322, 324,
326) may be plated or deposited (e.g., electroplating) with a
material identical to or compatible with NiP layer 315, such that
recessed zones (322, 324, 326) become filled to a level comparable
to the top surface of raised zones (321, 323, 325). Then, as
illustrated by FIG. 3F, the remaining segments of embossable layer
320 may be removed, for example, by chemical etching so that only
NiP layer 315 remains. Upon removal of embossable layer 320, zones
322, 324, 326 that were once recessed zones are now raised zones
that form the data zones of the NiP layer 315. Analogously, zones
321, 323, 325 that formed the raised zones (until plating recessed
zones 322, 324, 326 at FIG. 3E) are now the recessed zones
positioned between raised data zones 322, 324, 326 of the DTR
pattern as illustrated by FIG. 3F.
[0043] In an alternative embodiment, raised zones 322, 324, 326 of
FIG. 3F may be formed by first depositing a NiP material over the
imprinted embossable layer 320 (e.g., at FIG. 3D) by various
deposition methods such as chemical vapor deposition (CVD),
sputtering, and ion beam deposition. Next, the embossable layer
material may be selectively removed by any number of etching
methods described herein (e.g., chemical etching). In doing so, any
NiP material deposited above the embossable layer becomes "lifted
off," resulting in the raised zones (322, 324, 326) and recessed
zones (321, 323, 325) of FIG. 3F.
[0044] FIG. 3F shows the final raised zones (322, 324, 326)
textured. Unlike the method described with respect to FIGS. 2A-2G,
texturing NiP layer 315 prior to depositing embossable layer 320
would not preserve the textured areas in the final raised zones
(322, 324, 326). The texturing methods described above may be used
(e.g., mechanical and laser texturing). It should also be noted
that various cleaning and/or polishing operations may be performed
between the stages discussed above. For example, one or more
polishing operations (e.g., fine/kiss, coarse) may be performed to
remove asperities from the surface of one or more of the layers.
With NiP layer 315 now patterned and textured with a discrete track
recording pattern, other layers (e.g., a magnetic layer, lamination
layer) may be disposed above NiP layer 315 to form a longitudinal
or perpendicular magnetic recording disk.
[0045] The process of forming a discrete track recording pattern
illustrated in FIGS. 2A-2G differs from the process illustrated and
described in FIGS. 3A-3F in that the former forms the recessed
zones of the NiP layer by etching into the NiP layer to remove
material making up the NiP layer. The initial stamping of the
embossable layer serves as a template corresponding to the raised
and recessed zones. In the method described and illustrated by
FIGS. 3A-3F, the initial recessed impressions formed by a stamper
(e.g., recessed zones 322, 324, 326 shown in FIG. 3C) form what
eventually becomes the raised data zones 322, 324, 326 (as shown in
FIG. 3F). As such, the stamper utilized to form the impression
shown in FIG. 3C may form wider recessed zones compared to the
raised zones because ultimately, the recessed zones that become the
raised data zones of the NiP layer should be wider than the
recessed zones.
[0046] FIGS. 4A-4G show expanded cross sectional views illustrating
an exemplary embodiment of a method of forming a discrete track
recording pattern on a substrate for a magnetic recording disk. For
clarity of explanation, the various layers illustrated in FIGS.
4A-4G are exemplary and may not be scaled to representative sizes.
As discussed above, materials such as glass may be used for the
disk's substrate. Substrate disks constructed of materials such as
glass may not have a NiP plating because the material itself
provides mechanical support for subsequent texturing, polishing,
and/or patterning processes. With such substrates the discrete
track recording pattern may be formed directly in the substrate.
The method of forming the DTR pattern in a substrate may be
analogous to the subtractive method discussed above with respect to
FIGS. 2A-2G (i.e., for patterning a NiP layer). As shown in FIG.
4A, the patterning process begins with a disk-shaped (e.g., glass)
substrate 405. Disk substrate 405 may then be polished and
planarized. In one embodiment, disk substrate 405 may be polished,
for example, by a uniform etch. In alternative embodiments, other
polishing techniques may be used. Alternatively, disk substrate 405
may not be polished. Next, as illustrated in FIG. 4B, disk
substrate 405 may be anisotropically textured with a pattern, by
various methods as discussed above. Alternatively, as discussed
below, texturing of disk substrate 405 may be performed after the
discrete track recording pattern has been formed.
[0047] Next, as illustrated by FIG. 4C, disk substrate 405 may then
be coated with an embossable layer 420, for example, with a
photoresist, an electron sensitive resist, or other embossable
materials. Spin coating, dip coating, and spray coating are just
some methods of disposing the embossable layer 420 on substrate
405. Other coating methods and other embossable layer materials, as
discussed above, may be used.
[0048] Next, as illustrated by FIG. 4D, embossable layer 420 is
imprinted with a pattern of recessed zones (422, 424, 426) and
raised zones (421, 423, 425). The stamping of embossable layer 420
may utilize, for example, nanoimprint lithography techniques that
are well known in the art. In one embodiment, a stamper (not shown)
bearing a discrete track recording pattern, may be used to imprint
embossable layer 420 to form recessed zones (422, 424, 426) and
raised zones (421, 423, 425). Because of the thickness of the
embossable layer 420, the imprint of raised and recessed zones are
not likely to press into substrate 405. The stamper used to pattern
the embossable layer 420 has the inverse, or negative replica, of
the desired pattern (i.e., the discrete track recording pattern on
substrate 405) to be formed.
[0049] Next, as illustrated by FIG. 4E, embossable layer 420 may be
etched to further define the alternating recessed zones (422, 424,
426) and raised zones (421, 423, 425) that form the basis for the
discrete track recording pattern on substrate 405. In one
embodiment, a series, or step-wise process of etching procedures
may be performed on embossable layer 420 and substrate 405 to form
the desired track pattern. Embossable layer 420 serves as a stencil
to expose the substrate 405 in areas beneath the recessed zones
(422, 424, 426) of the pattern formed by the stamper. In one
embodiment, plasma etching is utilized to remove embossable layer
420 material in recessed zones (422, 424, 426) down to the
substrate 405. Alternatively, other etching methods may be used to
remove embossable layer 420 material in at least the recessed
zones, for examples, chemical etching, electron beam (e-beam)
etching, ion-beam etching (passive or reactive), sputter etching,
and plasma etching with reactive gases. For certain types of
etching (e.g., chemical), embossable layer material may be removed
from both the raised zones (421, 423, 425) and recessed zones (422,
424, 426) at approximately a similar rate. Chemical etching will
remove the embossable layer 420 in both the recessed zones (422,
424, 426) and raised zones (421, 423, 425) until substrate 405 is
exposed in the recessed zones (422, 424, 426), as illustrated by
FIG. 4E.
[0050] Next, as illustrated by FIG. 4F, recessed zones (422, 424,
426) of substrate 405 may be further etched (e.g., by chemical,
e-beam, ion-beam, and sputter etching). In one embodiment, the
etching of recessed zones (422, 424, 426) may not penetrate
completely through substrate 405 such that substrate 405 forms a
continuous pattern of recessed zones (422, 424, 426) and raised
zones (421, 423, 425). Having achieved a desired recess depth, the
remaining embossable layer 420 on the raised zones (421, 423, 425)
of the discrete track recording pattern may then be removed, for
example, by the methods discussed above in relation to FIG. 4E. The
removal of embossable layer 420 exposes the entire top surface of
substrate 405, as illustrated by FIG. 4G.
[0051] It is noted that raised zones (421, 423, 425), corresponding
to the data recording zones of the magnetic disk may be textured at
this stage, rather than texturing the entire substrate 405 prior to
coating with embossable layer 420 as discussed above in relation to
FIG. 4B. The texturing methods described above may be used (e.g.,
mechanical and laser texturing). As discussed above, substrate 405
may be textured before any imprinting or etching (e.g., as
described with respect to FIG. 4B). As previously noted, various
cleaning and/or polishing operations may be performed between the
various stages. With substrate 405 now patterned and textured with
a discrete track recording pattern, layers (e.g., a magnetic layer)
may be disposed above substrate 405 to form a longitudinal or
perpendicular magnetic recording disk.
[0052] FIGS. 5A-5F show expanded cross sectional views illustrating
an alternative embodiment of forming a discrete track recording
pattern on a substrate of a magnetic recording disk. This method
involves an additive process in which a material compatible or
identical to material forming the substrate is added or plated to
form the raised zones of the discrete track recording pattern. The
various layers illustrated in FIGS. 5A-5F are exemplary and not
scaled to proper sizes so that the process of patterning the
substrate may be described with clarity.
[0053] The additive process illustrated by FIGS. 5A-5F is analogous
to the subtractive process illustrated by FIGS. 4A-4G with respect
to the stamping and etching of the embossable layer 520 disposed
above substrate 505. As illustrated by FIG. 5A, the process begins
with substrate 505. Unlike the subtractive process described above,
substrate 505 is not necessarily textured at this point. As will be
apparent below, this method requires texturing of the final raised
zones of substrate 505 after the discrete track recording pattern
is formed
[0054] As illustrated by FIG. 5B, disk substrate 505 may then be
coated with an embossable layer 520, for example, with a
photoresist, an electron sensitive resist, or other embossable
materials. Spin coating, dip coating, and spray coating are just
some methods of disposing the embossable layer 520 on substrate
505. Other coating methods and embossable layer materials may be
used as discussed above. Next, as illustrated by FIG. 5C, a stamper
(not shown) bearing a discrete track recording pattern, may be used
to impress embossable layer 520 to form recessed zones (522, 524,
526) and raised zones (521, 523, 525). If the embossable layer 520
is thick relative to the depth of the pattern in the stamper, the
imprint from the stamper is not likely to register deep enough to
reach substrate 505. Alternatively, if embossable layer 520 is
relatively thin, it may be stamped to leave very little embossable
material in the recessed zones (522, 524, 526). Subsequently,
embossable material in the recessed zones (522, 524, 526) may be
removed to expose substrate 505. The stamper used to pattern the
embossable layer 520 may have a pattern identical to the pattern to
be formed on substrate 505.
[0055] Next, as illustrated by FIG. 5D, embossable layer material
in the recessed zones (522, 524, 526) may be removed by a number of
etching methods (e.g., by chemical, plasma, e-beam, ion-beam, or
sputter etching), such that surface areas of substrate 505 are
exposed. For certain types of etching (e.g., chemical), embossable
layer material may be removed from both the raised zones (521, 523,
525) and recessed zones (522, 524, 526) at approximately a similar
rate. Chemical etching will remove the embossable layer 520 in both
the recessed zones (522, 524, 526) and raised zones (521, 523, 525)
until substrate 505 is exposed in the recessed zones (522, 524,
526), as illustrated by FIG. 5D.
[0056] Next, as illustrated by FIG. 5E, recessed zones (522, 524,
526) may be plated (e.g., electroplating or electroless plating)
with a material identical to or compatible with substrate 505, such
that recessed zones (522, 524, 526) become filled to a level
comparable to the top surface of raised zones (521, 523, 525).
Then, as illustrated by FIG. 5F, the remaining segments of
embossable layer 520 may be removed, for example, by chemical
etching so that only substrate 505 remains. Upon removal of
embossable layer 520, zones 522, 524, 526 that were once recessed
zones are now raised zones that form the data zones of substrate
505. Analogously, zones 521, 523, 525 that formed the raised zones
(until plating recessed zones 522, 524, 526 at FIG. 5E) are now the
recessed zones positioned between raised data zones 522, 524, 526
of the DTR pattern, as illustrated by FIG. 5F.
[0057] In an alternative embodiment, raised zones (522, 524, 526)
of FIG. 5F may be formed by first depositing a substrate material
over the imprinted embossable layer 520 (e.g., at FIG. 5D) by
various deposition methods as discussed above. Next, the substrate
material may be selectively removed by any number of etching
methods described herein (e.g., plasma etching). In doing so, any
substrate material deposited above the embossable layer becomes
"lifted off," resulting in the raised zones (522, 524, 526) and
recessed zones (521, 523, 525) of FIG. 5F.
[0058] FIG. 5F shows the final raised zones (522, 524, 526)
textured. Unlike the method described with respect to FIGS. 4A-4G,
texturing substrate 505 prior to depositing embossable layer 520
would not preserve the textured areas in the final raised zones
(522, 524, 526). The texturing methods described above may be used.
As also previously noted, various cleaning and/or polishing
operations may be performed between the stages. With substrate 505
now patterned and textured with a discrete track recording pattern,
other layers (e.g., a magnetic layer, lamination layer) may be
disposed above substrate 505 to form a longitudinal or
perpendicular magnetic recording disk.
[0059] FIG. 6 is a cross section illustrating one embodiment of a
longitudinal magnetic recording disk 600 having a patterned NiP
layer 620 disposed above disk substrate 610. In one embodiment, a
textured discrete track pattern is generated on NiP layer 620, as
discussed above. After the patterned NiP layer 620 is textured
(e.g., by the methods described above with respect to FIGS. 2A-2G
or 3A-3F), additional layers such as a magnetic layer 630 may be
formed above NiP layer 620 to generate a magnetic recording disk.
In one embodiment, one or more layers 625 may also be disposed
between NiP layer 620 and magnetic layer 630 (e.g., an underlayer
and/or an intermediate layer) to facilitate a certain
crystallographic growth within the magnetic layer 630. For example,
an intermediate layer and/or an underlayer may be deposited on NiP
layer 620 to provide a surface on which magnetic layer 630 may be
epitaxially grown to control crystal morphology and orientation for
obtaining a two dimensional isotropic media. These layers may be
composed of materials to provide reasonably good lattice match to
the material used for the magnetic layer 630. Such layers are known
in the art; accordingly, a detailed discussion is not provided.
[0060] The disk 600 may also include one or more layers 640 on top
of the magnetic layer 630. For example, a protection layer (e.g.,
layer 640) may be deposited on top of the magnetic layer 630 to
provide sufficient property to meet tribological requirements such
as contact-start-stop (CSS) and corrosion protection. Predominant
materials for the protection layer are carbon-based materials, such
as hydrogenated or nitrogenated carbon. A lubricant may be placed
on top of the protection layer to further improve tribological
performance, for example, a perfluoropolyether or phosphazene
lubricant. Protection and lubrication layers are known in the art;
accordingly, a detailed discussion is not provided.
[0061] FIG. 7 is a cross section illustrating one embodiment of a
longitudinal magnetic recording disk 700 having a patterned
substrate 710. In one embodiment, a textured discrete track pattern
is generated on substrate 710, as discussed above. After the
patterned substrate 710 is textured (e.g., by the methods described
above with respect to FIGS. 4A-4G or 5A-5F), additional layers such
as a magnetic layer 730 may be formed above substrate 710 to
generate a magnetic recording disk. In one embodiment, one or more
layers 720, 725 may also be disposed between substrate 710 and
magnetic layer 730 (e.g., an underlayer and/or an intermediate
layer) to facilitate a certain crystallographic growth within the
magnetic layer 730. For example, an intermediate layer and/or an
underlayer may be deposited on substrate to provide a surface on
which magnetic layer 730 may be epitaxially grown to control
crystal morphology and orientation for obtaining a two dimensional
isotropic media. These layers may be of materials to provide
reasonably good lattice match to the material used for the magnetic
layer 730. Magnetic layers are known in the art; accordingly, a
detailed discussion is not provided. The disk 700 may also include
one or more layers 740 on top of the magnetic layer 730. For
example, a protection layer (e.g., layer 740) may be deposited on
top of the magnetic layer 730 to provide sufficient property to
meet tribological requirements such as contact-start-stop (CSS) and
corrosion protection.
[0062] A substrate having a discrete track recording pattern may be
used in perpendicular magnetic recording systems. In perpendicular
magnetic recording systems, the recorded bits are arranged as
antiparallel magnets in relation to one another, and are recorded
normal to the surface plane of the magnetic medium. Obeying the
pull of magnetic poles, recordings are attracted in high recording
density cohesion instead of demagnetizing. In contrast,
conventional longitudinal magnetic recording systems demagnetize
under repulsive forces. A perpendicular magnetic recording system,
therefore, has a larger recording capacity compared to a
longitudinal magnetic recording system. Perpendicular magnetic
recording systems typically include a hard magnetic recording layer
and a soft magnetic underlayer which provide a flux path from the
trailing write pole to the leading opposing pole of the writer.
FIGS. 8A-8B show expanded cross sectional views illustrating an
exemplary embodiment of a method of depositing a soft magnetic
underlayer on a patterned substrate. FIG. 8A shows a substrate 805
having a discrete track recording pattern formed therein. In one
embodiment, the patterned substrate 805 may be formed by the
subtractive process described above with respect to FIGS. 4A-4G. In
an alternative embodiment, the patterned substrate 805 may be
formed by the additive process described above with respect to
FIGS. 5A-5F. In another embodiment, patterned substrate 805 may
also be textured (e.g., as shown above by 405, 505). FIG. 8B shows
a soft magnetic underlayer 810 deposited on patterned substrate
805. Soft magnetic underlayer 810 may be deposited thinly enough on
substrate 805 to preserve the pattern of the recessed zones (i.e.,
track grooves). The soft magnetic underlayer 810 may be disposed
over substrate 805 by any one of the deposition methods described
above.
[0063] FIG. 9 is a cross section illustrating one embodiment of a
perpendicular magnetic recording disk 900 having a patterned
substrate 910. A discrete track pattern is generated on substrate
910, as discussed above. After a soft magnetic underlayer 920 is
deposited on substrate 910, additional layers such as a magnetic
layer 930 may be formed above substrate 910 to generate a
perpendicular magnetic recording disk. One or more layers 925 may
also be disposed between substrate 910 and magnetic layer 930
(e.g., an intermediate layer) to facilitate a certain
crystallographic growth within the magnetic layer 930. These layers
may be of materials to provide reasonably good lattice match to the
material used for the magnetic layer 930. The disk 900 may also
include one or more layers 940 on top of the magnetic layer 930.
For example, a protection layer (e.g., layer 940) may be deposited
on top of the magnetic layer 930 to provide sufficient property to
meet tribological requirements such as contact-start-stop (CSS) and
corrosion protection.
[0064] In one embodiment, the disk substrate 910 that is used to
generate a perpendicular magnetic recording disk 900 may be
textured, for example, to improve signal to noise ratio (SNR) and
thermal stability of the magnetic recording disk. The texturing of
a substrate for both longitudinal and perpendicular magnetic
recording disks may improve SNR and thermal stability by enabling
control of crystallite size and crystallite size variance in the
film layers deposited over the substrate. Although there are
contributions to SNR from the disk drive electronics and the
channel used to process the magnetic signal, there is also
intrinsic noise from the media, itself, that should be minimized. A
large contribution to the media noise is generated from the
inter-particle (or inter-crystalline) magnetic exchange interaction
that may be suppressed by isolating the magnetic crystals from each
other by one or more nonmagnetic elements or compounds. However,
another source of intrinsic media noise is the crystalline size and
variance of the magnetic grain. The texturing of a substrate for
both longitudinal and perpendicular magnetic recording disks may
improve control of crystallite size, spacing, and variance of the
grains in the film layers (e.g., intermediate layer, underlayer,
and/or nucleation layer) deposited over the substrate and, thereby,
the magnetic layer.
[0065] In an alternative embodiment, the soft magnetic underlayer
disposed above the disk substrate may be polished and/or textured.
The soft magnetic underlayer may be textured with a pattern, by
various methods such as mechanical texturing using fixed or free
abrasive particles (e.g., diamond). Alternatively, other types of
texturing methods, such as laser texturing, may be used to texture
the soft magnetic underlayer. In one embodiment, the texturing of
the soft magnetic underlayer may be in addition to the texturing of
a NiP layer disposed above the substrate. In an embodiment where
the NiP layer is absent, the substrate may be polished and/or
textured. In yet another embodiment, a thin NiP layer may be
disposed on soft magnetic underlayer and polished and/or textured.
A polished and/or textured NiP layer may be in addition to a
(polished and/or textured) NiP layer disposed above the
substrate.
[0066] FIG. 10 illustrates a disk drive having a disk (e.g., disk
600 700, or 900). Disk drive 1000 may include one or more of the
disks 1030 to store datum. The disk(s) 1030 resides on a spindle
assembly 1060 that is mounted to drive housing 1080. Datum may be
stored along tracks in the magnetic recording layer of a disk. The
reading and writing of datum is accomplished with head 1050 that is
used to alter the properties of the magnetic layer. A spindle motor
(not shown) rotates spindle assembly 1060 and, thereby, the disk
1030 to position head 1050 at a particular location along a desired
disk track. The position of head 1050 relative to disk 600 may be
controlled by position control circuitry 1070.
[0067] In the foregoing specification, the invention has been
described with reference to specific exemplary embodiments thereof.
It will, however, be evident that various modifications and changes
may be made thereto without departing from the broader spirit and
scope of the invention as set forth in the appended claims. The
specification and figures are, accordingly, to be regarded in an
illustrative rather than a restrictive sense.
* * * * *