Extendibility of Granular Oxide PMR Media · 1 Diskcon Asia Pacific 2006 Komag Inc. 1710 Automation...
Transcript of Extendibility of Granular Oxide PMR Media · 1 Diskcon Asia Pacific 2006 Komag Inc. 1710 Automation...
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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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
Plan-view TEM Image Of Perpendicular Media
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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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.
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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:
Diskcon Asia Pacific 2006
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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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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Diskcon Asia Pacific 2006
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.