Extendibility of Granular Oxide PMR Media · 1 Diskcon Asia Pacific 2006 Komag Inc. 1710 Automation Parkway San Jose, CA 95131 Extendibility of Granular Oxide PMR Media Asia Pacific

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Diskcon Asia Pacific 2006

Komag Inc.1710 Automation Parkway

San Jose, CA 95131

Extendibility of Granular Oxide PMR Media

Asia Pacific Diskcon, March 8-9, 2006, Singapore

Gerardo Bertero

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Outline of PresentationOutline of Presentation

•• State of the Art Granular Oxide PMR MediaState of the Art Granular Oxide PMR Media

•• Media Improvement OpportunitiesMedia Improvement Opportunities

•• Media Qualification Challenges with PMR TechnologyMedia Qualification Challenges with PMR Technology

•• SummarySummary

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Cross-Section TEM Image of PMR Media

Exchange Layer

Seed Layer

Overcoat Layer

Adhesion Layer

Soft Underlayer

Soft Underlayer

Nucleation Layers

Recording Layers

Substrate

-150 -100 -50 0 50 100 150-30

-20

-10

0

10

20

30

m (m

emu/

cm2 )

H (Oe)

Radial Circum.

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Plan-view TEM Image Of Perpendicular Media

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SNR Progression of Granular Oxide Media

20

15

10

5

SNR

(dB

)

605550454035302520151050

Time (Months)

- 6 dB

+ 12.4 dB

- CoCrPtB Media - CoCrPtO Media

Dec. 2000 Oct. 2005

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PMR Media Improvements

• SUL domain noise does not seem to be a problem with SAF SUL structures.

• C-axis orientation is already very good.

• Physical grain size is rather small in current media.

• Magnetic grain size is optimized by adding intergranular exchange.

Where can we expect improvements to come from ?

Given the above,

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PMR Media Improvement Opportunities

• SUL Domain and Magnetic Noise Reduction• SAF SUL Structure improvements• Domain free SULs

• Grain Size Uniformity• DC noise reduction• Narrower transition parameter

• IL Thickness Reduction• Better writability Higher Hc• Sharper head field gradients Narrower transition parameter

• Better Magnetic Exchange Management(E.g., CGC Media/Exchange Spring Media)• Narrower transitions, better DC noise, better writability

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SUL Technology

Domain Free SUL:

While we don’t intend to incorporate this feature in our first generation media, we have developed a simple, manufacturablestructure that enables us to achieve single-domain SULs.

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Hard Bias SUL

-200 -100 0 100 200-40

-20

0

20

40

Hex = 39.5 OeHc = 10.5 Oe

m (m

emu/

cm2 )

H (Oe)

RadialCircum

-2000 -1000 0 1000 2000-40

-20

0

20

40

Hswitch = 939 Oem (m

emu/

cm2 )

H (Oe)

DownUp

MINOR LOOP

FULL LOOP

Nucleation Layer(e.g., CrX)

Hard Magnetic Layer(e.g., CoCrTa)

SUL

Ru

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Typical Magnetic Domains in SUL Structures

Single SUL CoTaZr

HB SULCoCrTa/Ru/CoTaZr

SAF SULCoTaZr/Ru/CoTaZr

-150 -100 -50 0 50 100 150-30

-20

-10

0

10

20

30

m (m

emu/

cm2 )

H (Oe)

Radial Circum.

-150 -100 -50 0 50 100 150-2

-1

0

1

2

M (m

emu)

H (Oe)

Radial Circum

-150 -100 -50 0 50 100 150-30

-20

-10

0

10

20

30

m (m

emu/

cm2 )

H (Oe)

Radial Circum

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Nucleation Layer

• Main purpose is to:• Break magnetic exchange between SUL and Recording layer• Control recording layer crystallogrphic orientation• Control recording layer grain size• Help with recording layer grain isolation

• We use a triple layer NL structure (Ta/RuX/RuY)• These new NLs provide smaller magnetic grain

sizes and more magnetic grain isolation.• Overall NL thickness is still large.• Need to develop a robust < 10 nm process

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Exchange Decoupling of Magnetic Grains

Ru layer only(from different sample)

2 3

2 3

With RuX/RuY we observe smaller and well-separated Rugrains which result in better isolation at the magnetic nucleation stage.

Effective Gap Length is 2 x (Flight Height + Mag Layer Thickness + Intermediate Layer Thickness)

SUL

Mag L.ILIL

FHML

Mx x, y( ) = −Mx x,−y( )My x,y( ) = My x,−y( )

Image fields:


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Interlayer Thickness ReductionWith IL thickness reduction we expect:

• Stronger writing fields• Sharper write field gradients• Higher OW• Higher SNR

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Interlayer Thickness Effect – Parametric Performance

10 15 20 25 30 35 4045

50

55

60

OW

2 (dB

)

IL (nm)10 15 20 25 30 35 40

13

14

15

16

SNR m

e (dB

)

IL (nm)

10 15 20 25 30 35 404.0

4.5

5.0

5.5

6.0

6.5

7.0

I A/2 (m

V)

IL (nm)10 15 20 25 30 35 40

1200

1300

1400

1500

1600

Sign

alLF

(µV)

IL (nm)

-13.3%

Why ?

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Crystallographic C-axis Orientation

10 15 20 25 30 35 401.8

2.1

2.4

2.7

3.0

3.3

FWH

M (

degr

ee)

Interlayer thickness (nm)

Lorentz fit Ru (00.2) Co (00.2)

θ-2θ XRD FWHM at Rocking curves

40 41 42 43 44 450

50000

100000

150000

200000

250000

Co(00.2)

Ru(00.2)

Inte

nsity

(cou

nts)

2theta (degree)

S7261 RS#16 IL Cell 81 14 nm Cell 83 20 nm Cell 85 26 nm Cell 87 32 nm Cell 89 38 nm

SNR degrades with thinner IL but FWHM is still quite good

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Optimizing Echange in Granular Media

Intergranular exchange coupling is key for overwrite, SNR and nucleation field optimization. However, each of these properties optimize at different points so, tradeoffs must be made when optimizing media performance as a whole. Various approaches and schemes have been proposed to facilitate this task, e.g.,

• Capping layer media• Coupled granular composite media, CGC • Exchange coupled composite media, ECC

The capping layer approach is the most practical for performance and manufacturability

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Capping Layer Effect

S6651

-150

-100

-50

0

50

100

150

-20000 -15000 -10000 -5000 0 5000 10000 15000 20000

S7176

-100

-75

-50

-25

0

25

50

75

100

-20000 -15000 -10000 -5000 0 5000 10000 15000 20000

Hc (Oe) S* Hn (Oe)5000 0.45 -1900

Hc (Oe) S* Hn (Oe)5100 0.58 -2936

Nucleation field improvement for ATI robustness

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Capping Layer Analysis

Managing Intergranular Exchange Coupling

MAG1 MAG2Cell A 11 nm 0.00 nm

Cell B 11 nm 3.75 nm

Cell C 11 nm 8.25 nm

MAG 1: Higher O

MAG 2: Lower O

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HR TEM images of Cells A, B and C

Cell BCell A

Cell C4 5 6 7 8 9 10 11 12 13

05

101520253035404550

C11 C14 C20

Num

ber f

requ

ency

(cou

nts)

Grain size (nm)

Cell A Cell B Cell C

Grain size (nm) 7.38 7.80 8.68

Standard deviation (nm) 0.92 0.91 1.03

ABC

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Media Qualification Challenges

• Availability of product heads early in the process is not possible.

• Most times heads are not available either because of confidentiality issues or because of their design is changing rapidly.

• Hence, initially all of the feedback with product head comes frequently only from the customer.

• With PMR recording, heads and media are much more interdependentthan with LMR.

• Understanding of drive margins, channels, codes, etc., is key during final stages of optimization process.

• Without close collaboration with drive integrator, a successful qualification is next to impossible.

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Summary

• Currently we are focused on both performance and manufacturability aspects of PMR media.

• Much improvement in grain size, intergranular exchange, SUL noise and c-axis dispersion has already been accomplished.

• Opportunities for SNR improvement remain with IL thickness reduction mainly (must have appropriate heads to take advantage of such improvement).

• Given the head and media strong interactions with PMR recording, need to work closely with customers to identify other areas of improvement based on specific needs.

Documents

Extendibility of Granular Oxide PMR Media · 1 Diskcon Asia Pacific 2006 Komag Inc. 1710 Automation Parkway San Jose, CA 95131 Extendibility of Granular Oxide PMR Media Asia Pacific