current progress in discrete track recording (dtr) … r&d / confidential current progress in...

Komag R&D / Confidential

Current Progress in Current Progress in Discrete Track Recording Discrete Track Recording

(DTR) Media(DTR) MediaOctober 25October 25thth, 2006, 2006

Komag, Inc.1710 Automation Parkway

San Jose, CA 95131

October 25, 2006 Komag Confidential 2

OutlineOutline• Discrete Track Recording (DTR) Concept

– Feature dimensions• DTR Project Goals

– Key Technology Requirements• Nano-Imprint Lithography (NIL) Overview

– Masters and Stampers– Process Steps and Tools

• Spin-coat• Bake• Imprint• Develop (ash)• Wet etch• Strip and Clean

• DTR LMR and PMR Process Results Overview– DTR LMR– DTR PMR

• Overview of Recording Results• Current Challenges for DTR Processes

DTR Land & Grooves

Slider


Substrate

Write & ReadHead

Conventional Media: Magnetic Read Width (MRW) ≅ 50% to 60% TPMagnetic Write Width (MWW) ≅ TP

DTR Media:Land-to-Groove Ratio ≅ 3 to 1MRW ≅ Land Width = 75% TPMWW ≥ Land Width

Discrete Track Recording (DTR) ConceptDiscrete Track Recording (DTR) Concept

Write Wide Write Wide -- Read Wide Read Wide ≥≥ Land WidthLand Width


0

100

200

300

400

500

600

700

0 100 200 300

ArealAreal Density vs. Track PitchDensity vs. Track Pitch

Track Pitch (nm)

Den

sity

(Gb/

in2 )

B.A.R. = 567


ArealAreal Density vs. Groove WidthDensity vs. Groove Width(land(land--toto--groove ratio: 3 to 1)groove ratio: 3 to 1)

0

100

200

300

400

500

600

700

0 20 40 60 80

Groove Width (nm)

Den

sity

(Gb/

in2 )

B.A.R. = 567


DTR Project GoalsDTR Project Goals

• Develop cost-effective processes and tools for manufacturing DTR (patterned) media.– Nano-Imprint Lithography (NIL) has been primary focus.

• Study the recording performance of DTR media.– Ideally requires recording heads optimized for DTR media

(i.e., MRW ≅ land width).

• Study the feasibility and value of pre-formatted servo in DTR media.– Test various pattern schemes

• Study the tribology and corrosion performance of DTR media.– Slider fly-height is affect by grooved structures.


Key Technology RequirementsKey Technology Requirements

• Masters/stampers– E-beam tool capable of uniformly mastering features widths sub 30 nm.– Ability to format complex servo patterns.– Ability to replicate single master into multiple stampers.

• Tooling to uniformly spin-coat polymer on both sides of a disk simultaneously.

• NIL– Tool (i.e., press) which can uniformly imprint both sides of a disk

simultaneously out to the disk edge with high through-put.– Polymer which supports high fidelity and fast imprint cycle.– Reliable mold release for many cycles

• Wet-etch process with minimal undercutting (anisotropic) in order tomaintain small feature dimensions.

• Post-etch polymer stripping and cleaning process for DTR media– Possibly requires grooves to be filled and planarized.


NanoNano--Imprint Lithography (NIL) Imprint Lithography (NIL) Processing of Substrate (Disk)Processing of Substrate (Disk)

Develop Polymer Mask

Imprint PolymerNi Stamper

NiP Substrate

Wet Etch Substrate

Strip Polymer

polymercoating


Mastering ProcessMastering ProcessUsing an rUsing an r--θθ ElectronElectron--Beam RecorderBeam Recorder

ElectronElectron--Beam ColumnBeam Column

ResistResist--CoatedCoatedSi WaferSi Wafer

AFM xAFM x--section of developed resist mastersection of developed resist masterDepth = 70 nmDepth = 70 nm FWHD = 30 nm FWHD = 30 nm Pitch = 150 nmPitch = 150 nm


Process Steps

Pre-coat disk cleaning and/or sputtering

Spin-coat disk with polymer

DTR Disk: NIL Process Steps

95 mm NiP disk coated with polymer on both sides from 17 mm radius to disk edge.

Disk Location

Polymer thickness(Å)

i.d. 599

m.d. 624

o.d. 639


Process Steps



Bake Polymer Coating

Imprint polymer (press)


Angle 0.2 1.5 2.70 47 43 4990 42 42 46

180 49 54 49270 52 51 52

Distance from Disk Edge (cm)225 nm TP Stamper

polymer-coated disk embossed at 150 nm pitch

Imprint IssuesContamination control

particlesdelaminated polymer

Selection of polymerlow temp imprintshort imprint time

Selection of elastomerdurabilitycompliance

Stampermold release agentcompliance durabilitycost

Imprint eccentricity

Imprinting to the disk edge

Isothermal Imprinting

Process cycle time (throughput)imprint depth (nm)


imprint time (sec)

imprint depth (nm)

imprint depth range (nm)

imprint depth (nm)

imprint depth range (nm)

105 48.0 ± 1.2 58.2 ± 3.075 46.5 ± 1.9 53.8 ± 3.845 43.0 ± 2.6 53.3 ± 1.515 43.6 ± 1.4 51.8 ± 4.42 39.8 ± 2.0 47.6 ± 3.9

Imprint Depth as a Function Imprint Depth as a Function of Imprint Timeof Imprint TimeImprint pressure = 1300 psi

Imprint temperature = 131 ºCRamp time to max. pressure = 15 sec

Imprint depth measured using AFM at m.d. of disk at 0º, 90º, 180º and 270º.

polymer X

Dynamic viscosity = 10±2 mPa·sTg = 115 ºC

Dynamic viscosity = 5±2 mPa·sTg = 115 ºC

standardimprint time

polymer Y


DTR Disk: NIL Process StepsProcess Steps




Imprint polymer (press)

Ash in O2 plasma to create polymer mask

Polymer Mask

Surface of Substrate

68-70/33

66-66/31

64-70/34

66-68/30

60-64/30

64-66/26

72-76/28

68-70/27

G (nm)/H (nm)at 42.5, 32.5,22.5 mm radii

Gap Width (G)

Polymer Height (H)


Process Steps




Imprint polymer

Ash in O2 plasma to create polymer mask

Wet etch Substrate

Strip polymer (chemical)

Clean disk


NiP surface (wobbled tracks)

Etched grooves

SEM of Etched NiP


NanoNano--Imprint Lithography (NIL) Processing of Imprint Lithography (NIL) Processing of NiPNiP Disk With Narrow Grooves at 225 nm Track Pitch (TP)Disk With Narrow Grooves at 225 nm Track Pitch (TP)

Develop Polymer Mask

Imprint PolymerNi Stamper

NiP Substrate

Wet Etch Substrate

Strip Polymer

polymercoating

52 nm

35 nm 37 nm

36 nm

59 nm

23 nm

57 nm

Imprinted polymer

Polymer mask

Etched-NiP disk


Overview of DTR LMR ProcessOverview of DTR LMR Process

DTR processing to form groovesWet-etch process is slightly anisotropic

horizontal etch ~ 1.5 × vertical etch

Clean textured NPP

Sputter Full Stack LMR Media

DTR LMR Process(etched-NiP)

etched-NiP Disk

Sputtered LMR film stack

Finished DTR LMR Disk

TEM x-section


Original Demo of DTR PMR StructureOriginal Demo of DTR PMR Structure

DTR processing to form groovesWet-etch process is slightly anisotropic

horizontal etch ~ 1.5 × vertical etch

Clean Polished NPP

Sputter Full Stack PMR Media with SAF SUL

DTR PMR Process(etched-NiP)

SAF Soft Underlayer (SUL)

Etched-NiP

NiP groove width/depth: 155 nm / 33 nm at 380 nm TP

Finished DTR PMR Disk

TEM x-section


Alternative DTR PMR ProcessAlternative DTR PMR Process

Sputter Interlayers + Hard Magnetic Layers + Carbon

Clean NPP

Sputter SAF Soft Underlayer (SUL)

DTR processing to form groovesWet-etch process is isotropic

horizontal etch ~ 2 × vertical etch

SULSUL

Ru

Ru

DTR PMR Process(etched-SUL)

195 nm 203 nm

34 nm

Etched-SUL

Etched-SUL

grooveland


Limitations of DTR PMR Limitations of DTR PMR EtchedEtched--NiPNiP and Etchedand Etched--SUL ProcessesSUL Processes

• Poor Groove Geometry (e.g., shallow side-wall angles in grooves due to thick sputter layers, particularly for the etched-NiP case).

• Difficult to achieve narrow grooves due to groove depth requirement for magnetic isolation (i.e., spacing loss) and nearly isotropic etching of grooves.

• Possible poor magnetic properties caused by groove structure in Soft Magnetic Underlayer (SUL) (e.g., circumferential magnetization of SUL).


Current Process Development Current Process Development For DTR PMRFor DTR PMR

Sputter Full Stack PMR Media on NPP(or without carbon)

Coat w/polymer

Emboss and Develop Polymer MaskWet Etch ONLY Hard Magnetic (HM) Layer

Strip Polymer/Clean(Sputter carbon)interlayers

seed layer

HM HM

SAF SUL

interlayersseed layer

HM HM

polymer polymer

SAF SUL

interlayersseed layer

Hard Magnetic Layers (HM)

SAF SUL

polymer


SEM and AFM of SEM and AFM of OffOff--Track and LandTrack and Land--Groove Area Groove Area

AFM of Etched-PMR w/CarbonTrack Pitch (TP) = 380 nm

landgroove

SEM of Etched-PMR w/CarbonTrack Pitch (TP) = 380 nm

Etched-PMR w/Carbon


NPP Disk

texture

Clean

DTR Process

Clean

Sputter

Spin Coat Disk w/Polymer

Emboss Disk w/Stamper

Develop Mask

Wet Etch Disk

Strip Polymer

DTR Disk Fabrication Process FlowDTR Disk Fabrication Process FlowDTR LMR Process DTR PMR Process

Sputter Disk(full stack)

DTR Process

Clean

Lube

NPP Disk

Clean


Recording TestsRecording TestsLocating DTR TracksLocating DTR Tracks

DTR tracks

Data track

DTR RegionContinuousFilm

ContinuousFilm

Effect of eccentricity on waveforms


-1250 -1000 -750 -500 -250 0 250 500 750 1000 1250Cross-Track Position (nm)

0

5

10

15

20

25

30

35

40

45Sl

ot S

NR

(dB

)

100 kFCI500 kFCI

Measured SNR vs. CrossMeasured SNR vs. Cross--Track PositionTrack PositionDTR LMR MediaDTR LMR Media

DTR Structure:DTR Structure:Land Width = 550 nmLand Width = 550 nmGroove Width = 250 nmGroove Width = 250 nmGroove Depth = 60 nmGroove Depth = 60 nm

Head Parameters:Head Parameters:MWW = 240 nmMWW = 240 nmMRW = 155 nmMRW = 155 nm



0

2

4

6

8

10R

esid

ual L

F Si

gnal

(μV)

ConventionalDTR

Residual LF Signal After OverwritingResidual LF Signal After OverwritingLand Width = 290 nmLand Width = 290 nmGroove Width = 250 nmGroove Width = 250 nmGroove Depth = 44 nmGroove Depth = 44 nm

MWW = 340 nmMWW = 340 nmMRW = 237 nmMRW = 237 nm



0

10

20

30

40

50

HF/

LF O

verw

rite

(dB

)

DTRConventional

Overwrite vs. CrossOverwrite vs. Cross--Track PositionTrack PositionFor DTR and NonFor DTR and Non--Patterned MediaPatterned Media

Land Width = 290 nmLand Width = 290 nmGroove Width = 250 nmGroove Width = 250 nmGroove Depth = 44 nmGroove Depth = 44 nm

MWW = 340 nmMWW = 340 nmMRW = 237 nmMRW = 237 nm

Land Width


AFM and MFM of AFM and MFM of OffOff--Track and LandTrack and Land--Groove AreaGroove Area

AFM Image MFM Image

off-track land

track lands

grooves

off-track land

grooves

track lands

AC demagnetized case

Etched-PMR w/o Carbon


DTR PMR MediaDTR PMR MediaSpectrum @ 150 KFCISpectrum @ 150 KFCI

0 100 200 300 400 500 600 700-50

-40

-30

-20

-10

0

10

frequency (MHz)

Spe

ctru

m (d

B)

Land

Groove

• Signal reduction is about 45 dB from land to groove.• No signal pickup from the grooves.


Servo Using Wobbled GroovesServo Using Wobbled Grooves

f1 = 720 nmf2 = 790 nm


SNR Concern with SNR Concern with Wobbled Servo BlocksWobbled Servo Blocks

• Wavelength:– Carrier = 400nm (127 KFCI); Wobble f1= 720 nm, f2=790 nm

• Example shown here is for readback from center of land.– Land-to-grove = 3:1; MRW = land width; wobble 0-p = 1/4 of TP.

0 1 2 3 4 5 6 7 8 9 10-80

-60

-40

-20

0

20

40

1/λ (1/um)

Side band is more than 20dB lower than Carrier

Spectrum


Spectral Side Bands Spectral Side Bands Due to Groove WobbleDue to Groove Wobble

0 50 100 150 200 250 300 350 400-50

-40

-30

-20

-10

0

10

20Pos=-16uIn.txt

Frequency MHz

Pow

er S

pect

alD

ensi

ty (d

B)

188 190 192 194 196 198 200 202

-30

-25

-20

-15Pos=-16uIn.txt

f0+f2 f0+f1

f0=165.8MHzf1 = 29.00 MHz λ1 = 726 nmf2 = 26.36 MHz λ2 = 799 nm

0 100 200 300 400-50

-40

-30

-20

-10

0

10

Write Carrrier Signal or DC-Erase Land Area To Detect Groove Wobble


DTR LMR MediaDTR LMR MediaExperimental DataExperimental Data

-30 -20 -10 0 10 20 30-35

-30

-25

-20

-15

-10

-5

0

5

10

15E5793L: Land:Groove=1:1

Write Position (uIn)

20Lo

g10

Am

plitu

de (

dB)

f0f0+f1f0+f2

• Read width is comparable to land width.• Side band signals peak at track edges which could be used to develop new servo schemes on DTR media. However, side band signals are more than 20 dB below the carrier.


Focus of DTR LMR DevelopmentFocus of DTR LMR Development

• Prototype DTR Disk with Servo Capability– DTR LMR Disk Specifications:

• 225 nm track pitch (113 kTPI)• 3:1 land-to-groove ratio (groove width ~ 56 nm)

SEM ofetched-NiP disk


Focus of DTR PMR DevelopmentFocus of DTR PMR Development

• Demo extendibility of DTR for PMR media with High Areal Density Storage Capacity– DTR PMR disk specifications:

• 150 nm track pitch (170 kTPI)• 3:1 land-to-groove ratio (groove width ~ 36 nm)

SEM of Etched-PMR w/CarbonTrack Pitch (TP) = 150 nm

Land-to-groove ratio ~ 1 using current Stamper


Current Challenges For Current Challenges For DTR DevelopmentDTR Development

• Fabrication of e-beam Masters and Ni stampers with sub 30 nm wide features.

• Demonstrate the capability to wet etch very narrow grooves in PMR media with adequate signal reduction. (e.g.,20 nm for 100 nm TP at a 3:1 land-to-groove ratio).

– Requires e-beam masters and stampers with features < 20 nm wide.– Requires optimization of NIL process conditions in order to maintain groove

uniformity and minimize line edge roughness.

• Availability of recording heads for DTR– Groove volume affects slider fly-height– MRW ≅ Land Width (e.g., ~112 nm at 150 nm TP for a 3:1 land-to-groove ratio)

• Corrosion/Tribology on etched-PMR disks– Do grooves need to be filled and planarized?

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