0410 dasher
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© 2008 Hitachi Global Storage Technologies
The Future of MagneticRecording Technology
Richard NewDirector of Research
April 11, 2008
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24/11/2008© 2008 Hitachi Global Storage Technologies
Agenda
Overview of Hitachi GST & San Jose Research Center
Technology Challenges for Magnetic Recording
Future Recording Directions
Patterned Media
Thermally Assisted Recording
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34/11/2008© 2008 Hitachi Global Storage Technologies
Consolidated figures for FY 2006, ended March, 2007
Revenue US$ 86,847 million
Operating Income US$ 1,547 million
Number of Employees 384,444
Consolidated Subsidiaries 934
Hitachi Ltd. Overview
日立の事業
US$ 86.8billion
15%18%
5%
29%12%
24%13%
Information & Telecommunication Systems
High Functional Materials
Logistics, Servicesand Others
Financial Services
Power & Industrial Systems
Digital Media & Consumer Products
Electronic Devices
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44/11/2008© 2008 Hitachi Global Storage Technologies
Hitachi Global Storage Technologies Overview
Hitachi Global Storage Technologies (GST) was formed when Hitachi Ltd.purchased the Storage Technology Division from IBM.
The hard disk drive operations from IBM and Hitachi Ltd. were combined andlaunched as a new company on January 1, 2003.
Revenues in 2006 of $4.9 billion, 33K employees worldwide.
US headquarters in San Jose, California.WW operations in 9 countries (R&D in US & Japan, manufacturing in China,Phillipines, Thailand, Singapore, Japan and US).
1.5K R&D employees, with industry’s largest patent portfolio.
2.5-inch3.5-inchEnterprise
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54/11/2008© 2008 Hitachi Global Storage Technologies
Hitachi GST Headquarters in San Jose, CA
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64/11/2008© 2008 Hitachi Global Storage Technologies
San Jose Research Center Staff
~100 permanent research staff >70% hold PhD degree Geographically diverse
50% NA; 25% EMEA; 25% Asia
15 Fellows of professional societies Wide range of technical disciplines
Hitachi San Jose Research Center : Our People
Technical Disciplines
Educational Institu tion
Educational Institution
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S t a n f o
r d U C
S D
U C B e
r k e l e
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L A
C a l t e
c h
S a n J o
s e S t a t
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I l l i n o i s
C o r n
e l l
G e o r
g i a T e
c h
H a r v a r d
M I T
R W T H
A a c h e
n
U n i v e
r s i t y
o f B
a s e l
U n i v e
r s i t y
o f T
o k y o
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74/11/2008© 2008 Hitachi Global Storage Technologies
San Jose Research Center Facilities
58,000 sq ft of lab space 15,000 sq ft of clean room space Recording head prototyping line Full nano-fabrication facility E-beam, optical litho, deposition, RIE,
mill, characterization, SEM. MEMS lab, model making / machining shop
Hitachi San Jose Research Center : Our Facilities
MEMS
Vacuum
Resist Apply / Strip / BakeExpose / Develop
Plating / Etching
E-beam PhotoCMP
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84/11/2008© 2008 Hitachi Global Storage Technologies
Agenda
Overview of Hitachi GST & San Jose Research Center
Technology Challenges for Magnetic Recording
Future Recording Directions
Patterned Media
Thermally Assisted Recording
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94/11/2008© 2008 Hitachi Global Storage Technologies
Areal Density Trend
0.1
1
10
100
1000
10000
1990 1995 2000 2005 2010 2015
Year product available (mobile)
A r e a l D e
n s i t y ( G b / i n
2 )
Hitachi/HGST
IBM/HGST
Quantum/Seagate
Toshiba
Fujitsu
Samsung
AFC-LMR
TMR
PMR
TFC
etc.MR he ad
thin f ilm m ediaPRML channel
etc.
GMR headsMEPRML channel
etc. Advanced PMR?
DTM
BPM
TAR
60% CGR
90% CGR25% CGR
60% CGR
20~60% CGR
CPP-GMR
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104/11/2008© 2008 Hitachi Global Storage Technologies
HDD Technology Challenges
Signal Processing
01010100101101
1010101010101001010101110101
10101101010010
01010101010101
Servo Mechanics
DataData
DataData
ServoServo ServoServo ServoServo
TMR
Magnetic Spacing
ElementMagnetic
Physical Spacing
MagneticFilmDisk Substrate
Overcoat
Head/Disk Spacing
All with high reliability, highperformance, low power, and forpennies per GB.
Decode the signal with very fewreadback errors (~10-11 Sector
Failure Rate).
Read the data back with high SNRand high resolution.
Store the data reliably for morethan 10 years.
Write sharp transitions in therecording medium.
Fly the head very close to therecording medium.
Center the recording head above
the data track.
Recording SystemRequirements:
Write Head
Read Head
I
Disk
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114/11/2008© 2008 Hitachi Global Storage Technologies
Servo Mechanics Challenges
• Reduce Disturbances – Motor Vibration – Airflow Management
• Increase Disturbance Rejection – Increased Mechanical BW
– External Vibration FeedForward
– Adaptive Servo Algorithms – Dual Stage Actuation
(milli or micro−actuator)
• Shock Resilience
Ai rf lowModeling
FDB Motors
G Shock
100
1000
2005 2006 2007 2008 2009 2010 2011 2012 2013
Year
k T P I
Patterned Media
Continuous Media
1000 kTPI Track pi tch = 25 nm NRRO Sigma = 0.6 nm
25% TPI CAGR
Large TPI jumpwith BPM
Suspension
Slider
RecordingHead
Microactuator
Micro Actuator
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124/11/2008© 2008 Hitachi Global Storage Technologies
Magnetic Spacing Challenges
Surface Topology & Overcoats Thermal Fly Height Control
1
10
100
1000
0.1 1 10 100 1000
Areal Density (Gb/in2)
M a g
S p a c i n g ( n m )
Magnetic Spacing ClearanceSlider Overcoat
Recession
Media OvercoatMagnetic Film
Lube
Disk Substrate
MagneticElement
TOH
Slider
Corrosion, Scratch resistanceMedia Overcoat
Scratch resistanceLubricant
Disk RoughnessTake Off Height
Lube Transfer ClearanceScratch resistanceSlider Overcoat
Slider ProcessRecession
Design Constraint(s)Magnetic SpacingComponent
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134/11/2008© 2008 Hitachi Global Storage Technologies
FlyHeight
The Recording Mechanism
TrackWidth
Disk RotatesThis Way
Hard MagneticRecording Layer (CoCrX granular alloy)
Exchange Break Layer
Soft Underlayer New DataOld Data
C u
r r e n t
WriteFlux
WriteHead
ReadHead
WriteWidth
ReadWidth
Readback
Signal
Voltageltime
Magnetization into the plane
SkewAngle
Pole Tip
1 0 111 0 110 0 1 0 0 0 0 1 0 0 11 0DetectedData
Magnetization out of the plane
Media
TopView
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144/11/2008© 2008 Hitachi Global Storage Technologies
Writeability, Thermal Stability, and SNR
50 nm50 nm
• To increase SNR, need small grains.
• Smaller grains are thermally unstable.
• To avoid thermal instability, increasegrain anisotropy Ku.
• This increases the medium coercivity andmakes the medium difficult to write.
Solutions:• Capped and exchange spring media.
• Work with larger ‘grains’: patterned media.
• Work with higher anisotropy: thermallyassisted recording (TAR).
CONVENTIONALCONVENTIONAL
MEDIAMEDIA
S i n g l e G r a i n
M a g n e t o s
t a t i c E n e r g y
Magnetization Angle
-90 0 90
EnergyBarrier
MagneticGrain
Problem: T k
V K
B
u
Magnetic Stability:
∝energy barrier
thermal energy=
anisotropy x volume
kB x temperature
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154/11/2008© 2008 Hitachi Global Storage Technologies
H = 0 H H H
Media Technology
Media Technology Challenges
• Reduce grain size (8-9nm -> 6-7 nm).
• Increase anisotropy (to maintain stability).
• Maintain high quality growth:
– Uniform grain size – Narrow switching field distributions.
• Reduce media layer thicknesses:
– Reduce head to media spacing
– Reduce head to SUL spacing
COC
Mag Layers
Underlayer
Seed Layer
Soft Underlayer (SUL)
Adhesion
Substrate
Mag Layer Granular StructureMedia Stack
ExchangeBreak Layer (EBL)
Soft Cap Layer
Mag Layer
Soft Cap Layer
Coupling Layer
Mag Layer
Capped Media Exchange Spring Layer (ESL) Media
History of Media Innovations
• Thin film media (early 1990’s)
• AFC longitudinal media (pixie dust) (2000)
• PMR capped media (2005)• Exchange spring media (2008)
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164/11/2008© 2008 Hitachi Global Storage Technologies
Read Head Sensor Technologies
CPP (CurrentPerpendicular
to the Plane)
CIP(Current In Plane)
N/A
CurrentGeometry
JohnsonMag Noise
Spin Torque
Johnson
Shot NoiseMag Noise
Johnson
Johnson
BarkhausenJohnson
Major NoiseSources
1 Tb/in2
(PMR)
100
Gb/in2
(PMR)
2Gb/in2
(LMR)
100Mb/in2
(LMR)
10Mb/in2
(LMR)
ArealDensity
GiantMR
CPP GMR2011
Tunneling
MRTunnel Valve2006
GiantMR
Spin Valve1997
AnisotropicMR
MR Sensor 1991
N/AThin-filmInductive
1979
MREffect
StructureSensor
TechnologyYear
Lead Lead
Hard Bias Hard Bias
NiFe FreeLayer
Spacer
NiFeX SAL
Shield
Shield
Insulator
Lead Lead
Hard Bias Hard Bias
AP Pinn edCo Layer
Cu Spacer
NiFe Free Layer
Insulator Shield
Shield
MgO Tunnel Barrier AP Pinn ed CoFeB Layer
CoFe/NiFe Free Layer
HardBias
Spacer
Insulator
Spacer
HardBias
Insulator
Shield
Shield
HardBias
Spacer
Insulator
Spacer
HardBias
Insulator
Shield
Shield
Cu Spacer
High spin-scattering Free Layer
High spin-scattering
Pinned Layer
Lead Lead
Shield
Shield
Bottom Shield
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174/11/2008© 2008 Hitachi Global Storage Technologies
Read Head Sensor Challenges
Read Head Challenges
• Small Geomerty – Track width – Shield spacing
• High Sensitivity (mV/Oe)∆V = iη (∆R/R) R
• Low Noise – Johnson Noise – Shot Noise (TMR) – Mag Noise
• Design Constraints
– 50 Ω < R < 500 Ω – Temperature Rise – Breakdown Voltage – Spin Torque Instability – Magnetic Self-Field
S e n s o r r e s i s t a n
c e ( Ω )
20nm22nm30nm32nm35nmShield Spacing
30 dB
27 nm
1000 Gb/in2
31 dB
35 nm
750 Gbit /in2
30 dB
20 nm
2000 Gb/in2
32 dB33 dBSNR
45 nm60 nmTrack Width
500 Gbit/in2300 Gbit /in2Requirement
Read Head Requirements
Migration to Low RA Sensors
Track Width (nm) (~ Stripe Height)
100
200
300
400
500
10 20 30 40 50 60 70 80
0.1 - m2
0.15 - m2
0.05 - m2
0.4 - m2 1 - m
2
TMR
Current ScreenCPP-GMR
Al l MetalCPP- GMR
Migration toLow RA Sensors
(RA Product)
Sensor ResistanceR = (RA / TW 2 )
00
TW
~TW
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184/11/2008© 2008 Hitachi Global Storage Technologies
e−
AMR, GMR and TMR Physical Mechanisms
AMR (CIP) GMR (CIP)
TMR (CPP)GMR (CPP)
NiFe
Mechanism : Spin orbit scattering.Resistance lower when current flowis parallel to the magnetization M.
Limitation : Surface scattering limitsfilm thickness to > 100 nm.
M
ΔR/R ~ 2%
t ~ 100 nm E
D(E)D(E)
EF
majority
electronsminority
electrons
Mechanism : Spin dependent scattering.With M1||M2, half the electrons (the majorityelectrons) have low scattering in both films.With M1 anti || M2, all electrons have highscattering in one of the films.It turns out that M1||M2.has lower resistance.
Limitation : CIP lead parasitic resistance.
e−
Mechanism : Spin dependent tunneling.FM1 imparts a spin polarization : more min conduction e−.When M1||M2, these min e− have more states to tunnel into.So M1||M2 is the lower resistance state.
Limitation : High resistance as sensor size shrinks.
Mechanism : Same as CIP GMR.No parasitic resistance problem.Low noise, but lower ΔR/R than TMR.
Limitation : Spin torque, and “mag
noise” due to thermal fluctuations in M.
ΔR/R ~ 10-15%
ΔR/R >= 100% (room temp)
ΔR/R ~ 10%
1991 1997
20062010?
low
scattering
high
scattering
e−
FM1CuFM2
M1
M2
FM1MgOFM2
M1
M2
FM1CuFM2
M1
M2
e−
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194/11/2008© 2008 Hitachi Global Storage Technologies
Future Readback Sensor Candidates
ExtraordinaryMagnetoresistance
Coulomb BlockadeMagnetoresistance
Magnetic TunnelTransistor
Spin FET
Spin AccumulationSensor
Tunneling AnisotropicMagnetoresistance
Physics:Lorentz force +electrostatics insemiconductor
/metalheterostructures
Solin et al,JVST B 21,3002 (2003)
Physics:Single electron
transport +spin dependentchemicalpotential
Wunderlichet al, PRL 97,077201 (2006)
Physics:Hot electron transport+ spin dependenttransmission Park et al,
JAP 98,103701 (2005)
Jedema et al,
APL 81,5162 (2002)
Physics:Spin polarized injectionand extraction +Rashba effect
Hall et al,APL 83,2937 (2003)
Giddings et al,PRL 94,127202 (2006))
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204/11/2008© 2008 Hitachi Global Storage Technologies
AppliedField
Extraordinary Magnetoresistance (EMR) Sensor
2 DEG
2005 EMR Device
2006Device
AppliedCurrent
MeasuredVoltage +
2 DEG
Metal Shunt
Current Density
-500 -400 -300 -200 -100 0 100 200 300 400 500
0.124
0.125
0.126
0.127
0.128
0.129
0.13
BApplied
[Gauss]
V 2 - 4
[ V ]
y = 6.2e-006*x + 0.13ΔVEMR~ 6 mV @ 650 Oe
ΔVEMR/ΔH ~ 6 μV/Oe
Linear Response with ΔR/R ~ CIP GMR
Noise still a problem : lower SNR than TMR.
External Field
Electrons
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214/11/2008© 2008 Hitachi Global Storage Technologies
Iterative Decoding (LDPC Decoding)
readback
samples
PR
equalizer Viterbi Plus
Error Filters
detected
data
RS ECC
decoder
readback
samplesSISO
detector
detected data
iteration
Parity Check Nodes
Bit Nodes
SISO
Detector
bit probabilities
LDPC
Decoder
Iterative DecodingIssues
• Implementation complexity,speed and latency.
• Decoding error floors.• Miscorrection detection.
• Burst correction.
PR
equalizer
LDPC
decoder
RS ECC
decoder
Parity
Post Proc
hard decisions (bits)
soft decisions (bit probabilities)
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224/11/2008© 2008 Hitachi Global Storage Technologies
Agenda
Overview of Hitachi GST & San Jose Research Center
Technology Challenges for Magnetic Recording
Future Recording Directions
Patterned Media
Thermally Assisted Recording
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234/11/2008© 2008 Hitachi Global Storage Technologies
Patterned Media
Conventional PMR Media
• Continuous granularrecording layer.
• Multiple grains per bit.
• Boundaries between bitsdetermined by grains.
• Thermal stability unit isone grain.
Bit Patterned Media• Highly exchange coupled granular media.
• Multiple grains per island, but each islandis a single domain particle.
• Bit locations determined by lithography.
• Thermal stability unit is one island.
Discrete Track Media
• Conventional PMR media,with patterned tracks.
• Multiple grains per bit.• Eliminates track edge
noise and increasestolerance to TMR.
• Thermal stability unit isstill one grain.
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244/11/2008© 2008 Hitachi Global Storage Technologies
Patterned Media Fabrication Process
PMR Media Deposition
Nanoimprint
Pattern Transfer (i.e. etch/mill intorecording layer)
Planarization
Lube and Burnish
Inspection
Media Fabrication Process
Rotary Stage E-BeamPatterning
Master Template
Fabrication
Template
Replication
Template Fabrication
Template Replication
One e-beammaster template
10,000 replicananoimprint molds
100,000,000 imprinteddisk substrates
Existing Processes
New Processes
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254/11/2008© 2008 Hitachi Global Storage Technologies
Thermally Assisted Recording (TAR)
• Using new magnetic media, heat isapplied for ease of writing data
• Heat media to record data but store andread data at normal temperature
• Enables use of very difficult to write high-energy media, which is more stable forwriting data
• May allow areal density in the
terabit/square inch range, similar topatterned media GMR laser
write coils
heat spot
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264/11/2008© 2008 Hitachi Global Storage Technologies
Thermally Assisted Recording (TAR) Challenges
• Development of new small grain high coercivitymedia with correct thermal properties.
• Recording head writer design with opticalwaveguide and near field source.
• Head-disk interface & contamination.
• Light coupling efficiency from laser, throughwaveguide and near field source.
• Spot size converter, polarization rotator.
• Power dissipation and thermal
management in the recording head.
• Cost of laser and assembly per slider.
• Thermal timing and side writing on neighboringtracks.
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274/11/2008© 2008 Hitachi Global Storage Technologies
HDD Future Technology Roadmap
Time
A r e a l D e
n s i t y
Longitudinal
Recording
130
1000?
5,000?
20,000?
Perpendicular Recording
Patterned Media (PM)(DTR & BPM)
Thermally Assisted Recording (TAR)Possibly combined with PM
• 50 Years• >50 Mill ion increase in areal densi ty
HDD Future Technology• Conventional PMR technology likely extendable to 1 Tb/in2 or more.• Magnetic storage technology extendable to very high areal densities.
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284/11/2008© 2008 Hitachi Global Storage Technologies
Changing Markets and Usage Requirements
New Applications
• Portable storage
• Near line storage
• Set Top Boxes/PVR
• Gaming
Emerging Technical Requirements
• Security Features (bulk encryption)
• Reduced power consumption for datacenters
New Storage Interfaces
New Competing Technologies
Continued Growth in CapacityRequirements
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294/11/2008© 2008 Hitachi Global Storage Technologies
Summary
The HDD industry is at a technologycrossroads.
Transition to future technologies will bemore difficult than transition from
longitudinal to perpendicular recording.
Faster rate of technology introduction.
• Many new technologies required to reach1 Tb/in2 in ~2011.
Technologies must be introduced whilereducing cost (average prices decliningabout 5% per year).
Magnetic recording technologycontinues to be very extendable, but
investing in the R&D and in newtechnology introduction is challenging.