HDD Technology Trends

Transcription

1 R e s e a r c h HDD Technology Trends Dr. Richard New Director of Research Hitachi Global Storage Technologies

2 HDD Technology Challenges Storage Technology Capabilities Storage Usage Requirements Storage R&D Investment

3 Areal Density Technology Challenges Recording System Requirements: Center the recording head above the data track. Fly the head very close to the recording medium. Write sharp transitions in the recording medium. Store the data reliably for more than 10 years. Read the data back with high SNR and high resolution. Decode the signal with very few readback errors (~10-11 Sector Failure Rate). All with high reliability, high performance, low power, and for pennies per GB. Servo Mechanics Data Data Servo TMR Servo Servo Signal Processing Head/Disk Spacing Magnetic Element Magnetic Spacing Physical Spacing Magnetic Overcoat Film Disk Substrate Read Head Write Head Write Head Disk

4 Servo Mechanics Challenges Servo Mechanics Challenges Reduce Disturbances Motor Airflow External Vibration Increase Disturbance Rejection Mechanical BW Servo Control Algorithms Seek/Settle Performance 1000 ktpi Track pitch = 25 nm NRRO Sigma = 0.6 nm 1000 Significant TPI jump with patterned media Patterned Media Continuous Media Year ktpi 25% CGR for TPI Aerodynamics features Micro Actuator Adaptive Servo Algorithms Suspension Slider Microactuator Recording Head

5 Fly Height (Head-Disk Magnetic Spacing) Magnetic Spacing Challenges Corrosion Scratch Resistance Lubricant Transfer to Slider Thermal Fly Height Control Roughness (Take Off Height) Mag Spacing (nm) Areal Density (Gb/in 2 ) Surface Topology & Overcoats Thermal Fly Height Control Magnetic Element Recession Slider Slider Overcoat Lube Magnetic Spacing Media Overcoat Magnetic Film Disk Substrate Clearance TOH

6 Conflicting Constraints: Writeability, SNR & Thermal Stability CONVENTIONAL MEDIA Magnetic Grain 50 nm Single Grain Magnetostatic Energy Energy Barrier Problem: To increase SNR, need small grains. Smaller grains are thermally unstable. To avoid thermal instability, increase grain anisotropy Ku. This increases the medium coercivity and makes the medium difficult to write Magnetization Angle Solutions: Soft cap layer to aid switching. Work with larger grains : patterned media. Work with higher anisotropy: thermally assisted recording (TAR). Magnetic Stability: energy barrier thermal energy anisotropy x volume k B x temperature = KuV k T B

7 Capped and Exchange Spring Media Capped Media Exchange Spring Media Capping Layer (Write assist layer) strong coupling Media Layer Exchange Break Layer Soft Under Layer Exchange Spring Layer Coupling Layer weak interlayer Media Layer coupling Exchange Break Layer Soft Under Layer Hard Layer Soft Layer H = 0 H H H Cap TEM MAG only Low exchange TEM Cap only High exchange Mag

8 Patterned Media 80 nm AFM MFM

9 Thermally-Assisted Recording (TAR) Using new magnetic media, heat is applied for ease of writing data Heat media to record data but store and read data at normal temperature Enables use of very difficult to write high-energy media, which is more stable for writing data Allows areal density in the terabit/square inch range, similar to patterned media GMR laser write coils heat spot

10 Read Sensor Technologies Read Head Challenges High Sensitivity (mv/oe) V = i η ( R/R) R = η ( R/R) V Low Noise Johnson Noise Shot Noise MagNoise Small Gap Spacing (High Resolution) Design Constraints Temperature Rise Breakdown Voltage Spin Torque Instability Magnetic Self-Field Recording Head Evolution CIP-GMR (Current-in-plane) GMR spin-valve Magnetic tunnel-valve CPP-TMR (Current-perpendicular-to-plane) I GMR spin-valve I Lead > 100 Gbit/in 2 Lead Shield > 300 Gbit/in 2? Shield Shield Shield CPP-GMR (Current-perpendicular-to-plane) I

11 Read Sensor Technologies Read Head Challenges High Sensitivity (mv/oe) V = i η ( R/R) R = η ( R/R) V Low Noise Johnson Noise Shot Noise MagNoise Small Gap Spacing (High Resolution) Design Constraints Temperature Rise Breakdown Voltage Spin Torque Instability Magnetic Self-Field Sensor resistance (Ω) TW PHYS =SH (nm) 0.4 Ω -μm 2 1 Ω -μm Ω -μm Ω -μm 2 CPP- GMR 0.05 Ω -μm 2 Spintronics? EMR? TMR TW PHYS =SH (nm) Requirement 100 Gbit/in2 500 Gbit/in Gbit/in2 Sensor size 100nm 50nm 30nm Sensitivity 1mV/ 200 Oe 1mV /150 Oe 1mV / 100 Oe SNR >25 db >25 db >25 db

12 New Readback Sensor Technologies? Extraordinary Magnetoresistance Physics: Lorentz force + electrostatics in semiconductor /metal heterostructures Magnetic Tunnel Transistor Spin Accumulation Sensor Solin et al, JVST B 21, 3002 (2003) Coulomb Blockade Magnetoresistance Physics: Single electron transport + spin dependent chemical potential Wunderlich et al, PRL 97, (2006) Physics: Hot electron transport + spin dependent transmission Spin FET Park et al, JAP 98, (2005) Physics: Spin polarized injection and extraction + Hall et al, Rashba effect APL 83, 2937 (2003) Jedema et al, APL 81, 5162 (2002) Tunneling Anisotropic Magnetoresistance Giddings et al, PRL 94, (2006))

13 Changing Market & Usage Requirements New Applications Portable storage Near line storage Set Top Boxes/PVR Gaming Emerging Technical Requirements Security Features Reduced Power Consumption for Data Centers New Storage Interfaces New Competing Technologies Continued Growth in Capacity Requirements

14 Summary Changing industry with new challenges from outside. Faster rate of technology introduction. Many new technologies required to reach 1 Tb/in 2 (in 2011 at 40% CGR). Technologies must be introduced while reducing cost (average prices declining about 5% per year). Magnetic recording technology continues to be very extendable, but investing in the R&D and in new technology introduction is challenging. May need to adopt more collaborative models of technology development.