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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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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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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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Hitachi GST Headquarters in San Jose, CA

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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

0

1

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3

4

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6

7

8

9

10

S t a n f o

r d U C

S D

U C B e

r k e l e

y U C

L A

C a l t e

c h

S a n J o

s e S t a t

e C M

U

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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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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Agenda




Patterned Media


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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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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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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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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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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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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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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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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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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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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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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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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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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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Agenda




Patterned Media


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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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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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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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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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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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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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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.

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