Achieving Tight sigmas in Bit Patterned Media

Transcription

1 Achieving Tight sigmas in Bit Patterned Media Dieter Weller Chief Technologist Seagate Technology Diskcon 2008, September 18, Santa Clara Acknowledgement 1 Tbit/in 2 patterned dots Team Seagate

2 Areal Density Progress (HDD) Commercial products: ~400 Gbits/in 2, 500 GB/2.5 Platter Demonstrations: ~ 610 Gbit/in 2 Research frontier: 1 10 Tbits/in 2 Areal Density (Gbit/in 2 ) E-3 1E-4 1E-5 1 Tbit/in Gbit/in 2 1 Gbit/in 2 1 Mbit/in 2 2kbits/in 2 MR Head Thin Film Disk PRML Channel ~ 90 GMR 10 Head years, Products, Lab Demos 40%?? 1E Date (year) ~100% Dieter Weller, Sept 18, 2008 Page 2 97 TMR Head 04 PMR Rec. 06 ~10 8 increase Technology Options: Longitudinal Perpendicular Discrete Track Discrete Bit Heat Assist

3 Why Bit Patterned Media (BPM)? BPM overcomes thermal stability/writeability limitations by maintaining large bit volume rather than by increasing the anisotropy and write field Modeling suggests excellent extendibility of up to 10 Tbpsi with new ECC media designs; need tight physical and magnetic sigmas (~5%) PMR Head technology is expected to be scalable Servo & Data are patterned at the same time Achieving Tight sigmas in BPM Dieter Weller, Sept 18, 2008 Page 3 3

4 Main Challenges Recording on Individual Lithographically predefined Islands Areal density Bit size Pitch size 1 Td/in nm 25 nm 10 Td/in 2 will not provide a 4 nm 8 nm lithography solution in Challenges: Achieving Lithography at target density Control of position, size and magnetic sigmas Synchronizing Write Head to predefined magnetic islands Low Cost Manufacturing 66 grains 1 island PMR BPM The semiconductor industry time for patterned media 245 Gbpsi; BAR~6.4 Achieving Tight sigmas in BPM Dieter Weller, Sept 18, 2008 Page 4

5 ITRS Roadmap 2007 DRAM Half-pitch Flash Half-pitch BPM timeframe Achieving Tight sigmas in BPM Dieter Weller, Sept 18, 2008 Page 5

6 1 Tb/in 2 staggered media design TP=50.8nm 25.4nm BL=12.7nm Staggering allows BAR>1 BAR=4 for above case! Rubin and B. D. Terris, US patent US B2 (2005); H. J. Rechter, A. Y. Dobin, and D. K. Weller, US patent US A1 (2007); Dieter Weller, Sept 18, 2008 Page 6 Dot spacing (nm) 25.4 Bit Length (nm) 12.7 Track pitch (nm) 50.8 Duty cycle 50% D (nm) 12.7 Thickness (nm) 16 H k (koe) 4.6 Interlayer (nm) 6 M s (emu/cc) 1000 σ Hk /H k 5% σ position /BL 5% σt iming /BL 5% σ D /D 5% geometry optimized fixed H.J. Richter, A. Dobin et al. Appl. Phys. Lett. 88, (2006)

7 Patterned Media Processes 1. Mastering Rotating ebeam Lithography Assisted Self Assembly EUV Interferometry? 2. Template Family Quartz for UV-imprint Ni or Si for thermal imprint 3. Nanoimprint Lithography (NIL) UV Cure Thermal High Pressure Other 4. Magnetic Island Formation Etch Substrate & Deposit media Ion Mill Media, Plate 5. Planarization Sputter Fill and Etch Back CMP 6. Metrology Specific to process control Specific to identifying defects Cost stamp Hard mask Magnetic Ru stack Flyability Resolution Throughput Verification Dieter 7 Weller, Sept 18, 2008 Page 7

8 Mastering: Electron-Beam Writer with Rotary Stage Formatter: The Formatter generates tracks and servo patterns Beam blanking and deflection is synchronized to the rotating stage Down track Blanking Deflection with Vendor E-Beam Column: Small beam spot High beam current Rotating, r-θ Stage: rpm tracked by optical encoder Linear translation in one radial direction tracked by laser interferometer Servo BPM Discrete Tracks or patterned Bits Page 8

9 Mastering: Electron-Beam Writer with Rotary Stage Lifted off Cr Dots 450 Gd/in 2 Overview 9 Page 9

10 30 nm-thick HSQ using VB6 HR xy 100kV Pitch= 30 nm (717Gd) Pitch= 24 nm (1.1Td) Pitch= 21 nm (1.5Td) Pitch= 18 nm (2.0Td) Dieter Weller, Sept 18, 2008 Page 10

11 Dot Size Uniformity and Placement Accuracy 8 7 ZEP Resist 8 7 HSQ Resist 6 6 Sigma (%) Pitch (nm) Interaixs Distance Sigma Interdots Distance Sigma Dots Size Sigma Sigma (%) Pitch (nm) Interaixs Distance Sigma Interdots Distance Sigma Dots Size Sigma Pitch (nm) Interaxis Distance Sigma (%) Interdots Distance Sigma (%) Dots Size Sigma (%) Pitch (nm) Interaxis Distance Sigma (%) Interdots Distance Sigma (%) Dots Size Sigma (%) % sigmas in pitch and size at Tb/in 2 dot densities are possible today with x-y e-beam lithography! Dieter Weller, Sept 18, 2008 Page 11

12 Beyond 1Tdpsi BPM Combining e-beam Lithography with Self-Assembly E-beam: pitch DBC: if ½ pitch 2x2=4x gain in AD if 1/3 pitch 3x3=9x if ¼ pitch 4x4=16x Release e-beam lithography pressure 2:1 3:1 Self-Assembling Resists - Thermodynamic Processes 4:1 5:1 Improve dots size sigma Enhance pitch resolution up to a factor of 4 at least!! Chemical pattern as guide to direct polymer self-assembly Dieter Weller, Sept 18, 2008 Page 12

13 1.3 Tdot/in 2 Epitaxial Assembled Dot Over Large Area (Ebeam pattern period: Copolymer period = 3:1) Dieter Weller, Sept 18, 2008 Page 13 Shuaigang Xiao & XiaoMin Yang

14 Pattern Densification and Rectification Density Multiplication and Improved Lithography by Directed Block Copolymer Assembly, Ricardo Ruiz, 1* Huiman Kang, 2 François A. Detcheverry, 2 Elizabeth Dobisz, 1 Dan S. Kercher, 1 Thomas R. Albrecht, 1 Juan J. de Pablo,2 Paul F. Nealey 2*, Hitachi GST and U Wisconsin 15 AUGUST 2008 VOL 321 SCIENCE Figure 2 from Ruiz et al. Increased emphasis on self assembly methods to mitigate e- beam hardware limitations Dieter Weller, Sept 18, 2008 Page 14

15 Nanoimprint Lithography (NIL) Cross-section of Imprinted Resist 250 Gdpsi NIL is a viable solution for low cost, mass production of BPM media Molecular Imprints UV Cure Process Other suppliers: EVG, Obducat, Toshiba. Dieter Weller, Sept 18, 2008 Page 15

16 Nanoimprint and Templates at 1 Teradot/in 2 The established ZEP/Cr lift-off process has demonstrated template fabrication at bit density of 1.1 Tdot/in 2 (24 nm pitch) using VB6 E-beam 500 Gd/in 2 imprinted resist 100 x 100 um 2 1 Td/in 2 6 Quartz BPM Template 1.1 Td/in 2 template 1 Tdot/in 2 Dieter Weller, Sept 18, 2008 Page 16

17 media after nanoimprint (NIL) resist Mask Mag layer Resist descum/mask open Media Patterning Subtractive Methods (example to the left): IBE (Ion Beam Etch) RIBE (Reactive Ion Beam Etch) Pattern transfer Mask strip 25 nm etched dots on 50 nm pitch Trench fill Planarization Carbon/lube/buff/glide Additive Methods: Substrate Patterning Plating TDK Process: Y. Soeno et al. IEEE TRANSACTIONS ON MAGNETICS, VOL. 39, NO. 4, JULY 2003 Dieter Weller, Sept 18, 2008 Page nm plated dots on 50 nm pitch 17

18 Materials Options Anisotropy Field, H K,I 5-10 koe Media thickness, δ nm Saturation Magnetization, M s ka/m Carbon [0002] IL SUL Interlayer Amorphous SUL CoX alloys Co/X (Pd,Pt) multilayers ECC type composite media for higher densities Achieving Tight sigmas in BPM Dieter Weller, Sept 18, 2008 Page 18

19 Magnetic Results for 250 & 500 Gdpsi IBE CoX 250 Gdpsi flyable disk 500 Gdpsi coupon SFD = 5% Unpatterned Patterned 0.0 Im(χ T ) -0.2 σ HK =4.5% -0.4 Data Fit: σ(h K )/<H K > ~ 4.5% H in-plane (koe) Size sigma = 4.8% Dieter Weller, Sept 18, 2008 Page 19

20 Summary Modeling of BPM suggest that 5-10 Tdpsi Recording is possible if tight sigmas (<5%) can be achieved Rotating stage ebeam combined with BCP assisted assembly rectification and multiplication has the potential to get us to ultimate dot densities Tight physical and magnetic sigmas appear to be possible at lower densities Forming magnetic islands with <5% magnetic sigmas and surface control (planarization) will be the key challenges moving forward Dieter Weller, Sept 18, 2008 Page 20

21 Thank you! Many steep challenges Achieving Tight sigmas in BPM Dieter Weller, Sept 18, 2008 Page 21