21-Cheng-Mag pole oxid activ energy eval › wp-content › ... › Magnetic...Evaluation.pdf ·...
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Biography Yuhang Cheng got his PhD degree from the department of Materials Science and Engineering, Huazhong University of Science and Technology, China, in 1997. AGer that, he worked in the fields of thin film, metallurgy, process development, failure analysis, and reliability. Currently, he is working at Seagate Technology as a Development Staff Engineer in the group of Reliability and Thermal Mechanical Design, division of Advanced Transducer Development (ATD). His work is focused on the reliability test metrology development, failure mode and failure mechanism invesPgaPon, reliability improvement, and new material development for next generaPon magnePc recording heads.
Transcript of 21-Cheng-Mag pole oxid activ energy eval › wp-content › ... › Magnetic...Evaluation.pdf ·...
Biography Yuhang Cheng got his PhD degree from the department of Materials Science and Engineering, Huazhong University of Science and Technology, China, in 1997. AGer that, he worked in the fields of thin film, metallurgy, process development, failure analysis, and reliability. Currently, he is working at Seagate Technology as a Development Staff Engineer in the group of Reliability and Thermal Mechanical Design, division of Advanced Transducer Development (ATD). His work is focused on the reliability test metrology development, failure mode and failure mechanism invesPgaPon, reliability improvement, and new material development for next generaPon magnePc recording heads.
MagnePc pole oxidaPon acPvaPon energy evaluaPon
Yuhang Cheng, ScoR Franzen, Mike Seigler
Seagate Technology 7801 Computer Ave S. Bloomington, MN 55439
ASTR 2014, Sep 10 -‐ 12, St. Paul, MN September 5, 2014 2
Area density needs for Hard Disk Drive
Area density predicPon for hard disk drive
Y. Shiroishi, et al., IEEE Tran. of Mag., 45(10)(2009)3816
𝐾↓𝑢 𝑉/𝑘↓𝐵 𝑇 >70 Ku: anisotropy energy density. V: grain volume. kB: Bozeman constant. T: temperature
Signal to noise ra-o (SNR):
What is Heat Assisted MagnePc Recording (HAMR)?
Ø GMR: Giant magnetoresistance.
Challenge for HAMR: Pole oxidaPon
Ø Light absorpPon à High temperature at the pole Pp.
Ø High temperature àPole oxidaPon. Ø WG: waveguide.
Mark H. Kryder, et al., Procedings of the IEEE, 96(11)(2008)1810 Challener et al., Nat. Photonics, 220 (2009)
Pole temperature
Ø Mo-va-on: • Development of pole oxidaPon acPvaPon energy evaluaPon for HAMR
heads. • Compare pole oxidaPon acPvaPon energy of two Head Over Coats (HOC).
Ø Experimental details • Equipment:
o Carbolite air oven (RT-‐500 °C) with high temperature uniformity.
• Head over coat (HOC): § 1) HOC1 § 2) HOC2
• Scanning Electron Microscipe (SEM) used to evaluate pole corrosion.
AcPvaPon calculaPon
K: rate constant or lifetime.
A: Arrhenius constant;
Ea: activation energy (eV) of the failure model;
T: testing temperature (° K);
KB: Boltzmann’s constant (8.6173x10-5 eV/°K)
Arrhenius equation:
𝑘=𝐴∙ 𝑒↑− 𝐸↓𝑎 ⁄𝐾↓𝐵 𝑇 ln (𝑘) = ln (𝐴) + 𝐸↓𝑎 /𝐾↓𝐵 ∙ 1/𝑇
Design of accelerated life Pme test Ø Pole temperature during operaPon:
o Difficult to measure pole temperature during operaPon due to small size of the pole Pp and interacPon with laser light.
o Modeling show pole temperature during operaPon is about 250-‐300 °C.
Ø Preliminary results of pole oxidaPon: o At temperature >350 °C/10min, pole oxidized completely. o Need to select temperature <350 °C.
Ø Sample size: 58 heads. Ø Thermal annealing parameters:
o 250 °C/0.5, 1.5, 3, 5, 9h. o 280 °C/10min, 0.5, 1, 2, 4h. o 310 °C/10min, 0.5, 1h.
Ø OxidaPon started at the pole edge, and then extended to the side wall. Ø HOC1 has beRer pole oxidaPon resistance than HOC2.
3h 5h 9h 16h
Heads annealed at 250°C
0.5h 3h 9h 1.5h
Ø OxidaPon started at the pole edge, and then extended to the side wall. Ø HOC1 has beRer pole oxidaPon resistance than HOC2.
0.5h 1h 2h 4h
Heads annealed at 280°C
10min 1h 2h 0.5h
Ø OxidaPon started at the pole edge, and then extended to the side wall. Ø HOC1 has beRer pole oxidaPon resistance than HOC2.
10min 0.5h 1h
Heads annealed at 310°C
10min 0.5h 1h
Failure rate at different Pme and temperature
Ø As compared with HOC2, HOC1 has much beRer gas barrier property.
HOC recipeAnnealing
temperature, °CFailure rate
Failure mode
Failure rate
Failure mode
Failure rate
Failure mode
Failure rate
Failure mode
Failure rate
Failure mode
Time, h 0.5 1.5 3 5 9HOC1 250 0 0 13.79 Edge 39.66 EdgeHOC2 250 0.00 6.90 Edge 63.79 Edge 100.00 Edge 100 Entire poleTime, h 0.17 0.5 1 2.00 4.00HOC1 280 0 7.02 Edge 29.82 Edge 80.70 Edge 100.00 EdgeHOC2 280 1.75 Edge 52.63 Edge 87.72 Edge 100.00 Edge EdgeTime, h 0.1667 0.5 1HOC1 310 16.07 Edge 83.93 Edge 96.43 EdgeHOC2 310 65.52 Edge 100.00 Edge
How to calculate acPvaPon energy?
Ø Life Pme distribuPon analysis. o Using Weibull distribuPon to fit the lifePme data at different
temperature. o Find the mean Pme to failure for the heads with different HOC at
different temperature.
Ø Calculate acPvaPon energy Ea using Arrhenius equaPon.
Arrhenius equation: ln (𝑘) = ln (𝐴) + 𝐸↓𝑎 /𝐾↓𝐵 ∙ 1/𝑇
Comparison of HOC1 and HOC2
HOC1
Ø Heads with HOC1 and HOC2 have similar pole corrosion acPvaPon energy. Ø HOC1 show much beRer gas barrier property than HOC2.
HOC2
HOC Beta B C Ea
HOC1 2.28 16400 2.46E-‐13 1.41
HOC2 2.54 14578 2.34E-‐12 1.26
Life of P
ole
Pole oxidaPon acPvaPon energy applicaPon
t1 and t2 : lifetime at temperature T1 and T2 AT: acceleration factor; Ea: activation energy (eV) of the failure model; KB: Boltzmann’s constant (8.6173x10-5 eV/°K) T1: acceleration testing temperature (°K); T2: pole temperature during operation (°K).
Ø Predict pole oxidaPon lifePme using acceleraPon tested data.
Ø Save tesPng Pme. Ø Compare different head over coat material.
Summary Ø A method for measuring magnePc Pole oxidaPon
acPvaPon energy for HAMR heads was successfully developed.
Ø The pole oxidaPon energy of HAMR head with HOC1 and HOC2 was measured to be 1.41 eV and 1.26eV.
Ø Heads with HOC1 shows much beRer gas barrier property than HOC2.
Ø Pole oxidaPon acPvaPon energy could be used to esPmate pole lifePme and to screen new HOC.
