Magnetic Data Storage with Patterned Media

Transcription

1 f r e e d o m t o i n n o v a t e f r e e d o m t o i n n o v a t e Magnetic Data Storage with Patterned Media Neil Robertson Hitachi Global Storage Technologies San Jose Research Center Sept 08 1

2 Technology Roadmap: In Flux Areal Density (Gb/sq.in.) % / yr Products thermal instability regime Demos 60% / yr Standard FF MR head PRML channel Thin film disk 100% / yr GMR head Perpendicular DTM? TAR? 2012 BPM BPTAR? 2

3 Patterned Media: Discrete Track vs. Bit Patterned Media Conventional PMR Media Continuous granular recording layer Multiple grains per bit Boundaries between bits determined by grains Thermal stability unit is 1 grain (~ 6 nm diam.) Discrete Track Media Conventional PMR media, with patterned tracks Multiple grains per bit Eliminates track edge noise and reduces adjacent track interference Thermal stability unit is still 1 grain (~ 6 nm diam.) Bit Patterned Media Highly exchange coupled granular media Multiple grains per island, but each island is a single domain particle Bit locations determined by lithography Therm. stab. unit is 1 island (~15 nm diam.) 3

4 Modeling a BPM Recording System pooled fabrication tolerance centroid jitter shape jitter pooled synchronization tolerance write synchronization jitter NRO, etc. areal density contours [Tb/in 2 ] σ print =3 nm switching field distribution of the islands Areal Density [Tb/in 2 ] 1 Tb/in 2 design example σh sw 1000 Oe grad(h eff ) 430 Oe/nm periods λ 1 =λ 2 =25.4 nm island size=17.9x17.9x8 nm 3 trenches γ 1 =γ 2 =7.4 nm E b 120 k B T disqualified region of parameter space due to readback jitter or thermal stability σ print =2 nm BER w =10-6 K 1 =2.7x10 5 J/m 3 realistic regime gradient of the effective write field profile thermal stability contours [K 1 V/k B T] at 300 K M. Schabes HGST 4

5 Bit Patterned vs. Discrete Track Media: Examples at 1 Tbit/in2 Bit Patterned Media (BPM) BAR =1 Pitch = 25nm, Island size =18nm Fabrication tolerance: 1σ ~ 1 nm (size and placement) Discrete Track Media (DTM) BAR=4 Pitch = 47nm, land size = 33nm, groove = 14nm Requires very fine grain media BAR = 4 This BAR places tough demands on write head field and the servo system to due to the high tpi Down track pitch = 13nm, Island size = 9nm Tolerance = 1σ ~ 0.5 nm (size and placement) Even more aggressive patterning 5

6 Making Pattern Media: Ahead of the ITRS Roadmap ITRS Roadmap DRAM ½ Pitch (nm) nm 193 nm immersion with water 193 nm immersion with water 193 nm immersion with other fluids EUV, ML2 DRAM FLASH The semiconductor industry will not provide a lithography solution in 32 EUV 193 nm immersion with other fluids & lenses 193 nm with innovative immersion with water Imprint, ML2 time for patterned media EUV Innovative 193 nm immersion Imprint, ML2, Innovative Technology Innovative Technology Innovative EUV, Imprint, ML2, BPM PATTERNED MEDIA Research Required Development Underway Qualification Production Continuous Improvement 6

7 Some numbers to contemplate islands per disk smaller and denser features than used by the semiconductor industry 10 9 disks per year far higher than the total wafers/year by the semiconductor industry Low cost target < $5 per disk (total disk cost) A completely different approach is needed different process / different equipment double sided 7

8 Prepatterned Servo track direction (circumferential) data tracks servo sector track ID Gray code Very precise servo features created along with data track islands Eliminates need for separate servowriting operation Leads to multiple feature sizes in patterning quad burst tracking pattern 8

9 Bit Patterned Media: A Potential Fabrication Overview Existing Processes New Processes Template Fabrication Rotary Stage E-Beam Patterning Directed Self-Assembly Master Template Fabrication Template Replication Media Fabrication Process Incoming disk substrate Deposition of magnetic layers Nanoimprint Pattern Transfer (i.e. Etching) Planarization Lube and Burnish 1 master (e-beam + self-assembly) 10,000 replicated nanoimprint templates Inspection 100,000,000 patterned disks 9

10 Technology Building Blocks for Patterned Media Want to look at what is needed for each of these key building blocks and show some examples of status. Will mainly use BPM as an example system but most of discussion is also relevant to DTM. Media Deposition Masks Patterning Lithography Metrology Planarization 10

11 Master Pattern Lithography Roadmap e-beam lithography e-beam prepattern + block copolymer self-assembly 300 Gbit/in 2 Write at twice the period 1 Tbit/in 2 pattern clean-up 1X density and self-assembly fills in the missing dots 4X density E. Dobisz - HGST R. Ruiz - HGST rotary stage e-beam e-beam + density multiplier Pattern density (Gbit/sq. inch) 11

12 Beyond E-Beam: Self-Assembly of Block Copolymers Poly(styrene-block-methylmethacrylate) (PS-b-PMMA) thin film Short range order: hexagonal close-pack Long range: disordered (without guiding) 12

13 Pattern Clean-Up and Density Multiplication E-beam-generated chemical contrast patterns for directed self-assembly Pattern Rectification or Clean Up (1:1) Interpolation for Density Multiplication (4:1) Take an imperfect e-beam pattern Write at twice the period 1X density and improve spot uniformity via self-assembly and self-assembly fills in the missing dots 4X density R. Ruiz, H. Kang, F. A. Detcheverry, E. Dobisz, D. S. Kercher, T. R. Albrecht, J. J. de Pablo, P. F. Nealey, Science 2008, 321,

14 Pattern Density Multiplication (4:1 Guiding) E-beam pre-pattern Block Copolymer 39 nm period 78 nm period Dot Size Distribution σs=35nm2 σp=22nm2 54 nm period 27 nm period σs=39nm2 σp=13nm2 Hitachi Global Storage Technologies R. Ruiz, H. Kang, F. A. Detcheverry, E. Dobisz, D.2008 S. Kercher, T. R. Albrecht, J. J. de Pablo, P. F. Nealey, Science 2008, 321,

15 Long-range order R. Ruiz, H. Kang, F. A. Detcheverry, E. Dobisz, D. S. Kercher, T. R. Albrecht, J. J. de Pablo, P. F. Nealey, Science 2008, 321, 936. Density multiplication. 1Tb/in 2 L s =54nm; L p =27nm, σ x = 1.8nm, σ y = 1.0 nm Pattern Transfer to create Si Pillars 15

16 UV-Cure Nanoimprinting: Process Steps Graphic: Molecular Imprints, Inc. Resist dispensing (ink jet) Thin template is bowed so initial contact in the center of the disk Capillary forces pull template into conformal contact with the disk Expose with UV light to cure the imprint resist Separate template from disk Etch 16

17 Nanoimprinting: Molecular Imprints Imprio 1100 Pitch = 76nm, 50nm resist thickness 300 Gbit/in 2 (50 nm period hcp) pattern 17

18 Nanoimprinting Requirements for Patterned Media Conformal full-disk (no stepping) imprinting of surface with imperfect flatness (65 95 mm diameter disks) Double-sided imprinting Single layer / no overlay / modest alignment (~10 um centering on disk) Mitigation of defects on both templates and imprinted disks High fidelity replication of nm-scale features with high aspect ratio Resist adhesion to disk Low-force release from template Template lifetime and template replication Resist etch resistance for pattern transfer Residual layer thickness and uniformity Resist etch selectivity for pattern transfer Clean removability of resist High throughput and low cost Industry: 1 billion(!) disks/year residual layer thickness substrate nanoimprint resist 18

19 Mask and Lithography: Key Requirements Masks (Some business model options here with vendors) High precision rotary e-beam tools Image multiplication methods (copolymers, side wall imaging ) BPM patterns with BAR > 1 Pattern transfer tooling for image into substrate Method to cheaply replicate the masters Metrology (image size, image shape, image placement, defects) Imprinting High speed double sided imprint tools Reasonable lifetime of templates Insensitivity to incoming defects/contamination Metrology (image size, image shape, image placement, defects) 19

20 Pattern Transfer Approach 1: Etched Substrate Island Trench 50 nm diameter islands 100 nm pitch Direct e-beam lithography Cr lift-off dots as hard mask Substrate RIE Blanket mag layer deposition Issues with substrate etch approach: GOOD: clean, fast etching (RIE) of friendly materials Si, SiO 2, Si 3 N 4 etch products volatile BAD: trench material is present possible noise source BAD: large topography (~40 nm) needs planarization 50 nm pitch J. Risner, O. Hellwig, E. Dobisz, D. Kercher - HGST 20

21 Approach 2: Etched Magnetic Film Hard Mask Material #2 Hard Mask Material #1 Co/Pd ML Underlayers Substrate 90 nm diameter islands 160 nm pitch Nanoimprint lithography RIE removal of resist residual layer RIE of hard mask layers RIE (or IBE) of magnetic layer Issues with mag layer etch approach: BAD: dirty, slow etching (IBE) of unfriendly materials Co, Pd, Ni, etc. redeposition of nonvolatile products GOOD: no trench material GOOD: less topography BAD: possible edge damage due to ion bombardment, Strip of masks directly on media 21

22 Media patterning: Key Requirements Patterning High Speed double sided etch tools (800 dph) Ability to deal with either patterned media or patterned substrate concept Selectivity between mask and media Multiple etch steps/processes insitu and all vacuum based A clean mask strip process without media damage Temperature rise/cooling issue at high etch rates No redeposition of etched material and or edge damage to features Uniform CD control and sharp feature profiles with multiple feature sizes End point control Metrology (image size, image shape, image placement, defects) 22

23 Head-Disk Interface: Motivation for Planarization Conventional Smooth Disk Patterned Disk ~5 nm flying slider motion FH sigma ~ 10% of FH disk surface FH falls sigma increases slightly insufficient clearance: crash Patterned Disk w/ Higher FH Planarized Patterned Disk Trenches filled ABS change to increase FH sigma increases further behaves like conventional smooth disk low FH and tight sigma Lowest possible flying height (FH) and tight sigma essential for high density recording 23

24 Planarization: Key Requirements Planarization Low cost Concepts Deposition and etch Spin on and etch CMP Excellent planarization with no residual material left of top of media that impacts magnetic spacing. Ability to deal with multiple feature sizes. Planarization material consistent with HDD environment No contamination Ability to deal with either patterned media or patterned substrate concept End point control Metrology (planarity, defects) 24

25 Metrology: Key Requirements (at 1 Tbit in/2) Huge volumes of parts of media and templates Features < 12nm, 2:1 aspect ratios Placement 1 sigma < 1nm Multiple types of materials/substrates (glass, polymer, media) Process control (CD, placement, profile control) Lithography Etch Planarization Defect control (10 13 features per disks) Over several size ranges Catch small repeating defects in master and daughters Catch random tool induced defects in timely fashion to allow correction Extendibility 25

26 Bit Patterned Media: Summary Patterned Media (both DTM and BPM) are potential solutions for extending the areal density growth of magnetic data recording beyond the approaching limits of conventional media Likely fabrication strategy Master pattern generation by high resolution e-beam lithography and self-assembly Pattern replication by UV-cure nanoimprint lithography (the only viable lithography solution) Etching of disk substrate or mag layer Tight fabrication tolerances required: small feature and sigmas High quality master template Pattern multiplication needed to go beyond e-beam lithography Nanoimprint requirements for patterned media fabrication Full-disk conformal imprinting on both sides High yield / low defect rate but no overlay required! Patterning tools are novel in terms of High throughput and dual sided processing Potentially difficult materials to etch in high density patterns Metrology Need new concepts given the volume of disks and minimum feature sizes in play Magnetic layer optimization (not discussed) DTM: Small grain media BPM: Tight switching field distribution (SFD) required 26