Recent Progress in the Patterned Media
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1 Workshop at U. AL Toshiba Kikitsu 1 Recent Progress in the Patterned Media A. Kikitsu , H. Hieda, M. Sakurai, Y. Kamata, and K. Naito Toshiba Corp., Corporate R&D Center OUTLINE: (1) Introduction (2) Fabrication process (3) Flyability / Flattening (4) Magnetic properties (5) Signal properties (6) Summary
Transcript of Recent Progress in the Patterned Media
1 Workshop at U. AL Toshiba Kikitsu1
Recent Progress in the Patterned Media
A. Kikitsu,H. Hieda, M. Sakurai, Y. Kamata, and K. NaitoToshiba Corp., Corporate R&D Center
OUTLINE: (1) Introduction(2) Fabrication process(3) Flyability / Flattening(4) Magnetic properties(5) Signal properties(6) Summary
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Introduction: concept of the patterned media
20 x 100 nm
patterned media:no thermal fluctuation
current medium:thermal fluctuation ofsmall magnetic grains
recording head
track
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data track
recording head
recording medium
magnetic dot;one-bit / dot
<8nm
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Challenging Issues:fabricationflyability / flattening
Engineering Issues:magnetic designpositioning / servosignal processing (synchronous writing)head design
R&D issues for the patterned media
R. White: IEEE Trans. Magn., 33 p.990 (1997)Nakatani: Japanese Pat. (1989)
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(1)fabrication process
highest barrier for the patterned mediadifficulties compare to the semiconductor process
- size ~ cutting edge technology- throughput ~ orders of faster
highest barrier for the patterned mediadifficulties compare to the semiconductor process
- size ~ cutting edge technology- throughput ~ orders of faster
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Fabrication (I) - basic design
substrate patterning☺no film etching process
(conventional process)☺high throughput☹pseudo patterned media
- magnetic layer in a groove☹difficulty for thick (perpendicular) media
substrate patterning☺no film etching process
(conventional process)☺high throughput☹pseudo patterned media
- magnetic layer in a groove☹difficulty for thick (perpendicular) media
magnetic layer patterning☺ideal patterned media☺any layer structure is acceptable☹low throughput & dust
magnetic layer patterning☺ideal patterned media☺any layer structure is acceptable☹low throughput & dust
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Fabrication (II) - examples of two designs
substrate pattering(KOMAG: DTM)
wet etching (Al/NiP sub.)
substrate pattering(KOMAG: DTM)
wet etching (Al/NiP sub.)
glass substrateunderlayer
magnetic dots
magnetic layer patterningion milling (CoPtCr layer)
magnetic layer patterningion milling (CoPtCr layer)
D. Wachenschwanz: IEEE magn., 41 p.670 (2005)
Y. Kamata: Intermag 06 GE-09
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Fabrication (III) - etching mask formation
- electron beam (EB) direct drawing- ion beam exposure through stencil mask-nano imprint lithography (NIL)
: advantage in mass production
- electron beam (EB) direct drawing- ion beam exposure through stencil mask-nano imprint lithography (NIL)
: advantage in mass production
P. R. Krauss and S. Y. Chou : J. Vac. Sci. Technol., B 13, p.2850 (1995)
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Fabrication (IV) - pattern drawing
Electron Beam Drawing: 50nm or less☺ arbitrary shape .. servo☹ time consuming
Self Assembling: ~10nm☺ simultaneous formation in a large area☹ tetragonal lattice☹ defects / domains -> artificial control
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nano imprinting
self-assembling
mastering byLBR / EBR
Example of mass production
stamper
etching(ion milling)
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Patterned media by a self assembled mask
after AC erase after DC erase
Naito et al.: IEEE Trans. Magn. 38,1949 (2002)
aligned CoCrPt dots; 40 nm
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(2)flyablity / flattening
key issue for high-density HDDflying height < 10nm;
no dust, no debris, no protrusionadditional process -> throughput issue
key issue for high-density HDDflying height < 10nm;
no dust, no debris, no protrusionadditional process -> throughput issue
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Flyablity / flattening (I) - current results
No flattening (substrate patterning: KOMAG)reduction in flying height but good flyabilty (TMRC 2004)
No flattening (substrate patterning: KOMAG)reduction in flying height but good flyabilty (TMRC 2004)
Filling & flattening:bias-sputtered SiO2 + etching back (TDK)
surface roughness: <0.4nmall-dry process - good productivity
Filling & flattening:bias-sputtered SiO2 + etching back (TDK)
surface roughness: <0.4nmall-dry process - good productivity
Hattori et al: IEEE Trans Magn.40 p.2510 (2004)
flying height fluctuation
continuous DTM
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Flyablity / flattening (II) - Toshiba
substrate / underlayer
SOG
CoCrPtC over coat
Y. Kamata: Intermag06 GE-09
SOG filling + etching backa few nm of protrusion
SOG filling + etching backa few nm of protrusion
SOG
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vibrating
lubricant adhesion
flat media (before etching)patterned media (SOG + etching)
Result of Flyablity test - Toshiba◆Ring head◆Nominal flying height : 19.5nm◆Rotation speed : 4200rpm
AE signal
no collision to dustsvibration by lubricant adhesion
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(3)magnetic properties
granular -> isolated uniform dotsstrong de-mag fieldmagnetization rotation
granular -> isolated uniform dotsstrong de-mag fieldmagnetization rotation
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Magnetic properties (I) - new feature
enhanced write margin ~ a half of the dot size- nucleation and almost coherent reversal
enhanced write margin ~ a half of the dot size- nucleation and almost coherent reversal
M. Albrecht: APL 81 p.2875(2002)
head
no reversal:< first half
reversal: > first half
no need ofwriting field
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Magnetic properties (II) - Hc distribution (Toshiba)
large switching field distribution in the patterned dotspossible origin:
uniformity (magnetic characteristics, crystal orientation)process damage, atomic distribution
-> common issue for nano-dot devices
Hc distribution of aligned CoCrPt dots(40nm )
dot-by-dot MFM analysis
0 – 0.50.5 – 1.01.0 – 1.51.5 – 2.02.0 – 2.52.5 – 3.03.0 – 3.53.5 – 4.04.0 – 4.54.5 – 5.05.0 – 5.55.5 – 6.06.0 – 6.5> 6.5
Hc0 – 0.5
0.5 – 1.01.0 – 1.51.5 – 2.02.0 – 2.52.5 – 3.03.0 – 3.53.5 – 4.04.0 – 4.54.5 – 5.05.0 – 5.55.5 – 6.06.0 – 6.5> 6.5
Hc
Y. Kamata: Intermag 06 GE-09
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(4)signal properties
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signal properties (I) - sharp magnetic transition
Ideal transition can be realized in the patterned media.Ideal transition can be realized in the patterned media.
-20 -10 0 10 20-1
-0.5
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Distance (nm)
Nor
mal
ized
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plitu
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Circle dot pattern (BL=20nm)Perpendicular (a=0)
0 0.5 1 1.50
0.2
0.4
0.6
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Density (MFCI)N
orm
aliz
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utpu
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Read Gs=30nm, spacing=10nm
Patterned (Dd/Dp=0.5)Step M Perp.(a=0) Perp. (a=5nm)
1T
2T
3T8T
normalized transitionbetter than ideal one (a=0)
roll-off curveresolution (=1T/8T) enhancement > 20%
numerical estimation: read circle dot (40nm) by 30nm-gap
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result of RW test (Toshiba)
MWW：850 nmMRW：600 nm
Trajectory of ring head
on-track off-track
0.5MHz (2kfci)
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progress of the patterned media- ☺fabrication
- substrate / mag. etching- nano-imprinting lithography- EB drawing / self assembling .. ~10nm
- ☺ flyablity / flattening .. proven by experiments- no flattening- bias sputtered SiO2 / SOG filling
- ☺ magnetic properties- benefit: wide write margin- distribution in the magnetic properties
- ☺ signal properties- ideal transition is expected
Summary and Conclusion (I)
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1990 1995 2000 2005 2010 2015
dens
ity (G
b/in
ch2 )
0.1
1.0
10
100
1000
60% AGR
30% AGR
thin film media 100% AGR
30% AGR
MR head
GMR head
Advanced long. media
Perp. media
DTM /BPM
Summary and Conclusion (II)
