Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland...
-
Upload
liliana-nash -
Category
Documents
-
view
212 -
download
0
Transcript of Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland...
![Page 1: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/1.jpg)
Challenges of cost effective screening of current and future TMR/PMR design heads
Henry Patland
President & CEO
www.us-isi.com
![Page 2: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/2.jpg)
AbstractAs the industry makes the transition to PMR technology, with expected 100% transition by 2010, there are many challenges that head designers need to overcome to make this transition successful.
In addition to dealing with completely new head, media and channel designs, head manufacturers have to quickly anticipate the type of failures they will see from new head designs in volume production environments and be ready to cost effectively screen out those failures.
This presentation will concentrate on the challenges of testing these new head technologies, the type of solutions that are currently available and future requirements. Also a cost effective test strategy will be presented for discussion.
![Page 3: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/3.jpg)
Outline GMR/LMR head technology overview TMR/PMR head technology overview Conventional quasi-static testing (QST) Specific problems for PMR/TMR heads Can QST testing address these specific problems for
TMR/PMR heads? Dynamic testing an alternative or complement to QST
testing Advantages/disadvantages of dynamic vs. QST testing Proposed cost efficient model for electrical head test Conclusion
![Page 4: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/4.jpg)
GMR/LMR Heads
![Page 5: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/5.jpg)
TMR/PMR
![Page 6: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/6.jpg)
LMR vs. PMR Recording
LMR head sees zero field between transition and either a positive or negative field during transition
PMR head sees either positive or negative field between transitions and zero field during transition
![Page 7: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/7.jpg)
LMR Transition Field Component
Structure of media stray field and read-back pulse for longitudinal recording
![Page 8: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/8.jpg)
PMR Transition Field Component
Media stray fields for perpendicular media with soft under-layer
U-Shape bending caused by Perpendicular Stray Field
![Page 9: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/9.jpg)
Low Frequency Cut-off in PMR
Read-back of low density perpendicular square wave pattern with different LF cut-off frequency: Signal shape distortions
![Page 10: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/10.jpg)
Conventional QST Testing of both GMR/LMR and TMR/PMR Heads
High/Low resistance Low amplitude High asymmetry Barkh jump, hysteresis Low SNR Instability ESD damage (pin-layer-reversal)
![Page 11: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/11.jpg)
QST Transfer Curve
Resistance
Amplitude
Asymmetry
Barkh Jump
Hysteresis
Bias Point
Delta R/R
Bias Angle
Slope
Max Slope
Parametrics extracted from QST Transfer Curve
![Page 12: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/12.jpg)
Field Induced Instability
Soft Kink at 160 Oe
![Page 13: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/13.jpg)
Field Induced Instability @ 150 Oe
![Page 14: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/14.jpg)
Field Induced Instability @160 Oe
![Page 15: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/15.jpg)
Field Induced Instability @ 170 Oe
![Page 16: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/16.jpg)
Spectral Maximum Amplitude Noise (SMAN) Test
Patent: US6943545
Soft Kink at 160 Oe
![Page 17: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/17.jpg)
Spectrum Analysis
![Page 18: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/18.jpg)
Pin-Layer-Reversal due to ESD damage
![Page 19: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/19.jpg)
QST has good track record at conventional testing.
Can QST testing address TMR/PMR Specific Problems?
![Page 20: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/20.jpg)
PMR/TMR Specific Problems and Using QST Test Strategy
Pin-holes and µSmearing on insulating spacer Instability with lower cut off frequency Weak pin-layer Stray side field sensitivity and larger shield
geometries Writer pole problems
![Page 21: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/21.jpg)
Problem: Pin-Hole & µSmearing Issues Both Pin-Holes and µSmearing occur during manufacturing of TMR
stacks with extremely thin insulation layer
Both Pin-Holes and µSmearing disrupt the tunneling mechanism and essentially create a short across the insulation layer
When Pin-Holes are present, some of the Bias current flows through the created shorts, and SNR is deteriorated
Additionally these shorts cause higher operating temperature of the TMR sensor which in turn causes reliability issues
Pin-Holes or µSmearing
![Page 22: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/22.jpg)
QST Solution: Pin-Hole & µSmearing Issues By raising the TMR sensor temperature either
through Bias Source or external means, and measuring the Resistance change, both Pin-Hole & µSmearing can be detected
DeltaR/R, Transfer Curve, Hysteresis, and Slope of Transfer Curve are also good indicators of Pin-Hole or µSmearing presence
![Page 23: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/23.jpg)
Problem: Lower Frequency Instability
Since PMR heads see more low frequency component and are exposed to multiple state magnetic fields between transitions, the probability of magnetic field induced instability is increased
This type of instability can cause high BER or losing servo in the drive
![Page 24: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/24.jpg)
QST Solution: Lower Frequency instability
By lowering the cut-off freq to 100Khz from typical 3-5Mhz and using industry standard Spectral Maximum Amplitude Noise (SMAN) tests these unstable heads can be effectively screened out
![Page 25: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/25.jpg)
Problem: Weakly Pinned Heads
If pinned layer is weak, the magnetization angle between pinned layer and free layer is compromised causing degraded DeltaR/R, SNR degradation and sensor instability
![Page 26: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/26.jpg)
QST Solution: Weakly Pinned Heads
By testing heads at high magnetic fields and various angles, weakly pinned head can be screened out by QST
Weakly pinned heads might require additional re-initialization before final QST test
![Page 27: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/27.jpg)
Problem: Stray Side Field sensitivity and New Larger Shield Geometries
Stray side field sensitivity can cause sensor saturation and transition shifts as caused by adjacent tracks
Larger shields absorb much of external magnetic field to shield the sensor and can also become magnetized causing sensor instability
![Page 28: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/28.jpg)
QST Solution: Stray Side Field sensitivity and New Larger Shield Geometries
By testing QST with different magnetic field orientation, stray side field sensitivity can be simulated and sensitive heads can be screened out
By applying larger magnetic fields (typ: TMR/PMR – 500 to 600 Oe) the larger shields can be saturated to conventionally exercise the sensor
![Page 29: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/29.jpg)
Problem: Writer Pole Design
Vertical Pole heads have poor write gradient
Write distortions when head is skewed with respect to track direction
Thin pole heads exhibit pole remnance problems due to magnetic domains in the pole tips (sometimes overwriting servo patterns)
![Page 30: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/30.jpg)
QST Solutions: Writer Pole Design
With current technology QST is not capable of detecting this failure
Currently through improved writer pole material and geometry design, this issue is getting resolved
![Page 31: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/31.jpg)
ISI Quasi-Static Testing Portfolio
![Page 32: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/32.jpg)
Available Electrical Test Technologies
Dynamic Testing Quasi-Static Testing
![Page 33: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/33.jpg)
Dynamic Head Test Advantages
Tests both writer and reader Resembles closely final head/media
arrangement Extensive tests such as MRR, Amp, Asym,
NLTS, SNR, OW, PW50, MRW, MWW, ATE, BER
![Page 34: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/34.jpg)
Dynamic Head Test Disadvantages
High capital cost ($$$) Low UPH (typical 30-40) Media quality/flying height variation Difficult to separate writer vs. reader failures Can only be done at HGA level, high scrap cost High operating cost Larger and higher class cleanroom required Higher ESD danger due to more handling Poor correlation to final HDD yield
![Page 35: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/35.jpg)
QST Head Test Advantages Low capital cost ($) High UPH (typical 1000) Can be done at row level (early test equals lower
scrap cost) Very detailed and effective reader testing with
and without various stresses Good correlation to final reader related HDD
Yield Low ESD risk due to automation Low operating cost Less clean room space and lower class
cleanroom required
![Page 36: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/36.jpg)
QST Head Test Disadvantages
Cannot characterize writer Cannot predict head/media interface problems
since there is no flying No off-track analysis
![Page 37: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/37.jpg)
Conventional Electrical Test Flow Model
100%
Bar/Slider
QST
100%
Dynamic Head Test
100%
Head Stack Actuator
QST
100%
Final HDD Test/Burn-in
![Page 38: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/38.jpg)
Conventional Electrical Test Cost Model
Annual Slider
Volume(M) Yield
Test Type
ASP(K)
Number of Testers
Required
Annual Cost /w
5 Yr Depr.(M)
Slider UPH
%Of
Sliders Tested
Cost per slider
%Of Total
Test Cost3,947 70% QST Wafer $750 221 $33 3000 100% $0.017 5.56%3,036 80% QST Bar $150 729 $22 700 100% $0.011 3.66%2,530 85% DET HGA $250 10,630 $532 40 100% $0.266 89.06%2,200 90% QST HSA $45 1,138 $10 325 100% $0.005 1.72%2,000Total $0.30
Final HDD Yield
Re-work Cost
AvgHds/HDD
HDD Total(M)
Total Rework
Cost(M)
98.00% $3.00 2.50 800 $48
Note:Assumes 17hr/day tester utilizationAssumes Rework Cost labor only
![Page 39: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/39.jpg)
Proposed Electrical Test Flow Model
100%
Bar/Slider
QST
5%
Dynamic Head Test
100%
Head Stack Actuator
QST
100%
Final HDD Test/Burn-in
Sampling or NO DET Testing
![Page 40: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/40.jpg)
More Cost-Effective Test Cost Model
Annual Slider
Volume(M) Yield
Test Type
ASP(K)
Number of Testers
Required
Annual Cost /w 5 Yr
Depreciation(M)
Slider UPH
%Of
Sliders Tested
Cost per slider
%Of Total
Test Cost3,947 70% QST Wafer $750 221 $33 3000 100% $0.017 35.93%3,036 80% QST Bar $150 729 $22 700 100% $0.011 23.69%2,530 90% DET HGA $250 532 $27 40 5% $0.013 28.79%2,300 85% QST HSA $45 1,189 $11 325 100% $0.005 11.60%2,000Total $0.05
Final HDD Yield
Re-work Cost
AvgHds/HDD
HDD Total(M)
Total Rework
Cost(M)
95.00% $3.00 2.50 800 $120
Note:Assumes 17hr/day tester utilizationAssumes Rework Cost labor only
![Page 41: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/41.jpg)
Conclusion Even though the final HDD yield is lowered in
the Proposed Test Model the total cost of annual DET cost and rework cost combined is: $147M vs. $580M in the Conventional Test Model
Quasi-Static Test is the cost effective test solutions for current and future TMR/PMR design heads
Can 100% DET testing be cost-effective?
![Page 42: Challenges of cost effective screening of current and future TMR/PMR design heads Henry Patland President & CEO hpatland@us-isi.com .](https://reader038.fdocuments.us/reader038/viewer/2022110321/56649d015503460f949d38bc/html5/thumbnails/42.jpg)
References Alexander Taratorin, “Magnetic Recording Systems and
Measurements”, San Jose Research Center, HGST Bryan Oliver, Qing He, Xuefei Tang, and J. Nowaka), “Dielectric
breakdown in magnetic tunnel junctions having an ultrathin barrier”, JOURNAL OF APPLIED PHYSICS VOLUME 91, NUMBER 7
Sangmun Oh1, K. Nishioka2, H. Umezaki3, H. Tanaka1, T. Seki1, S. Sasaki1, T. Ohtsu2, K. Kataoka2, and K. Furusawa1 “The Behavior of Pinned Layers Using a High-Field Transfer Curve”, IEEE TRANSACTIONS ON MAGNETICS, VOL. 41, NO. 10, OCTOBER 2005
H. Patland, W. Ogle, “High Frequency Instabilities in GMR Heads Due to Metal-To-Metal Contact ESD Transients”, EOS/ESD Symposium 2002
Integral Solutions Int’l, “Quasi 97”, “Blazer-X5B” and “QST-2002” Tester