Recent Progress in the Patterned Media

Transcription

1 Recent Progress in the Patterned Media A. Kikitsu, H. Hieda, M. akurai, Y. Kamata, and K. aito Toshiba Corp., Corporate R&D Center OUTLIE: (1) Introduction (2) Fabrication process (3) Flyability / Flattening (4) Magnetic properties (5) ignal properties (6) ummary 1 1 Workshop at U. AL Toshiba Kikitsu

2 2 Workshop at U. AL Toshiba Kikitsu 2 Introduction: concept of the patterned media 20 x 100 nm patterned media: no thermal fluctuation current medium: thermal fluctuation of small magnetic grains recording head track data track recording head recording medium magnetic dot; one-bit / dot <8nm

3 R&D issues for the patterned media Challenging Issues: fabrication flyability / flattening Engineering Issues: magnetic design positioning / servo signal processing (synchronous writing) head design akatani: Japanese Pat. (1989) R. White: IEEE Trans. Magn., 33 p.990 (1997) 3 3 Workshop at U. AL Toshiba Kikitsu

4 (1) fabrication process highest barrier for the patterned media difficulties compare to to the semiconductor process --size ~ cutting edge technology --throughput ~ orders of of faster 4 4 Workshop at U. AL Toshiba Kikitsu

5 Fabrication (I) - basic design substrate patterning nofilm etchingprocess (conventional process) highthroughput pseudo patterned media --magnetic layer in in a groove difficulty for for thick (perpendicular) media magnetic layer patterning idealpatterned media anylayerstructureis acceptable low throughput & dust 5 5 Workshop at U. AL Toshiba Kikitsu

6 Fabrication (II) - examples of two designs substrate pattering (KOMAG: DTM) DTM) wet wet etching etching (Al/iP (Al/iPsub.) D. Wachenschwanz: IEEE magn., 41 p.670 (2005) Y. Kamata: Intermag 06 GE-09 magnetic layer patterning ion ion milling milling (CoPtCr layer) layer) magnetic dots underlayer glass substrate 6 6 Workshop at U. AL Toshiba Kikitsu

7 Fabrication (III) - etching mask formation --electron beam (EB) direct drawing --ion beam exposure through stencil mask -nano imprint lithography (IL) :: advantage in in mass production P. R. Krauss and. Y. Chou : J. Vac. ci. Technol., B 13, p.2850 (1995) 7 7 Workshop at U. AL Toshiba Kikitsu

8 Fabrication (IV) - pattern drawing Electron Beam Drawing: 50nm or less arbitrary shape.. servo time consuming elf Assembling: ~10nm simultaneous formation in a large area tetragonal lattice defects / domains -> artificial control 8 8 Workshop at U. AL Toshiba Kikitsu

9 Example of mass production etching (ion milling) mastering by LBR / EBR stamper nano imprinting self-assembling 9 9 Workshop at U. AL Toshiba Kikitsu

10 Patterned media by a self assembled mask aligned CoCrPt dots; 40 nm after AC erase after DC erase aito et al.: IEEE Trans. Magn. 38, 1949 (2002) Workshop at U. AL Toshiba Kikitsu

11 (2) flyablity / flattening key issue for high-density HDD flying height < 10nm; no no dust, no no debris, no no protrusion additional process -> -> throughput issue Workshop at U. AL Toshiba Kikitsu

12 Flyablity / flattening (I) - current results o flattening (substrate patterning: KOMAG) reduction in in flying height but good flyabilty (TMRC (TMRC 2004) 2004) Filling & flattening: bias-sputtered io2 io2 + etching back (TDK) surface roughness: <0.4nm all-dry process --good productivity flying height fluctuation continuous DTM Hattori et al: IEEE Trans Magn.40 p.2510 (2004) Workshop at U. AL Toshiba Kikitsu

13 Flyablity / flattening (II) - Toshiba OG filling + etching back a few nm of of protrusion OG OG substrate / underlayer Y. Kamata: Intermag06 GE-09 CoCrPt C over coat Workshop at U. AL Toshiba Kikitsu

14 Result of Flyablity test - Toshiba Ring head ominal flying height : 19.5nm Rotation speed : 4200rpm flat media (before etching) AE signal patterned media (OG + etching) no collision to dusts vibration by lubricant adhesion vibrating lubricant adhesion Workshop at U. AL Toshiba Kikitsu

15 (3) magnetic properties granular -> isolated uniform dots strong de-mag field magnetization rotation Workshop at U. AL Toshiba Kikitsu

16 Magnetic properties (I) - new feature enhanced write margin ~ a half of of the dot size --nucleation and almost coherent reversal head no reversal: < first half reversal: > first half no need of writing field M. Albrecht: APL 81 p.2875(2002) Workshop at U. AL Toshiba Kikitsu

17 Magnetic properties (II) - Hc distribution (Toshiba) large switching field distribution in the patterned dots possible origin: uniformity (magnetic characteristics, crystal orientation) process damage, atomic distribution -> common issue for nano-dot devices H c > 6.5 Hc distribution of aligned CoCrPt dots (40nm ) dot-by-dot MFM analysis Y. Kamata: Intermag 06 GE Workshop at U. AL Toshiba Kikitsu

18 (4) signal properties Workshop at U. AL Toshiba Kikitsu

19 signal properties (I) - sharp magnetic transition Ideal transition can be be realized in in the patterned media. numerical estimation: read circle dot (40nm) by 30nm-gap 1 1 8T Read Gs=30nm, spacing=10nm 3T ormalized Amplitude Circle dot pattern (BL=20nm) Perpendicular (a=0) Distance (nm) normalized transition better than ideal one (a=0) ormalized Output T Patterned (Dd/Dp=0.5) tep M Perp.(a=0) Perp. (a=5nm) Density (MFCI) roll-off curve resolution (=1T/8T) enhancement > 20% 1T Workshop at U. AL Toshiba Kikitsu

20 result of RW test (Toshiba) MWW:850 nm MRW:600 nm Trajectory of ring head 0.5MHz (2kfci) on-track off-track Workshop at U. AL Toshiba Kikitsu

21 ummary and Conclusion (I) progress of the patterned media - fabrication - substrate / mag. etching - nano-imprinting lithography - EB drawing / self assembling.. ~10nm - flyablity / flattening.. proven by experiments - no flattening - bias sputtered io2 / OG filling - magnetic properties - benefit: wide write margin - distribution in the magnetic properties - signal properties - ideal transition is expected Workshop at U. AL Toshiba Kikitsu

22 ummary and Conclusion (II) 1000 Perp. media density (Gb/inch 2 ) MR head thin film media 30% AGR 60% AGR GMR head Advanced long. media 100% AGR 30% AGR DTM /BPM Workshop at U. AL Toshiba Kikitsu