Quasi Static Testing Ultimate Solution for Cost Effective Quality Verification and ESD Analysis of GMR Heads

Henry Patland

Wade Ogle

2192 Bering DriveSan Jose, CA 95131

hpatland@isiguys.comwww.isiguys.com

Welcome to Complex World of GMR Head

Manufacturing GMR heads with good Yield, Reliability and Cost GMR is a new complex technology requiring new

manufacturing and test methodology

GMR technology provides huge advances in Arial Density

GMR is the most ESD sensitive mass produced device in

the world

Is There an ultimate test solution for manufacturing

GMR heads with good Yield, Reliability and Cost?

WAFER (Semiconductor Process, Test)

ROW/BAR(Wafer Slicing, Row Level Lapping, Test)

SLIDER(Row Dicing, Slider Level Lapping, Test)

HGA(Assy from Sliders, Suspension, FCBA’s, Test)

HSA(Assy from HGA’s, Actuator, VC, FCBA’s, Preamp Chip, Test)

HDA(Assy from HSA’s, Media, Enclosures, Drive PCB, Servo,Test)

How many places in your manufacturing process can GMR elements get damaged?

GMR Manufacturing Process

Basics of Quasi-Static TestingThe roots of QST are derived from actual drive operation

As GMR passes over a disk it is introduced to a variety of magnetic field.

In simplest terms the resistance of the GMR is dependent on the magnetic field applied to it.

In ideal case the relationship of GMR resistance to applied field is linear, but we don’t live in ideal world.

Close To Ideal Transfer Curve

QST Testing as a Concept

Independent of external influence (disk variation)

Significantly more flexible, with the ability to subject the GMR to any variety of operating conditions.

Can analyze pure GMR performance with higher resolution than DET Testing.

Reduced Risk of Handling or Tester damaging heads

QST Testing is inexpensive, fast, relatively simple, and requires significantly lower maintenance and operating costs compared to DET Testing.

Quasi Static Testing can characterize the GMR performance,

with the following advantages over DET Testing:

QST Transfer CurveResistance

Amplitude

Asymmetry

Barkh Jump

Hysteresis

Bias Point

Delta R/R

Bias Angle

Slope

Max Slope

Parametrics extracted from QST Transfer Curve

Common Anomalies which cause errors in a drive

Amplitude variation

Asymmetry

Baseline anomalies

Single Bit Jumps (Kinks)

Can QST screen out these Anomalies? Amplitude / Asymmetry Variation Baseline Shift / Popping Field Induced Instabilities (Kinks) Reader Induced Instabilities Writer Induced Instabilities ESD Soft/Hard Damage (Amplitude, Pin-Reversal,

Asymmetry) DET/Drive Correlation

Amplitude/Asymmetry Variation

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0

500

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Transverse Transfer C u rveB ia s : 4 .5 P a r t ID : A 2 0 - 1 8 H e a d : F a rH d 0

Am

plit

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e (

uV

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M agnetic F ield (O e)

Forward Reverse

Poor Amplitude

High Asymmetry

Base Line Shift / Popping

-3000

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0

1000

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3000

-300 -250 -200 -150 -100 -50 0 50 100 150 200 250 300

Transverse Transfer C u rve B ia s : 3 .9 7 8 P a r t ID : H e a d : 2

Am

plit

ud

e (

uV

)

M agnetic F ield (O e)

Forward Reverse

Large Hysteresis

Barkhausen Jump

Field Induced Instabilities

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0

500

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Transverse Transfer C u rveB ia s : 4 .5 P a r t ID : A 2 0 - 2 0 H e a d : F a rH d 0

Am

plit

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e (

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M agnetic F ield (O e)

Forward Reverse

314.0

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124.1149.5

174.9200.2

225.6

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276.4

301.8

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F ield (Oe)

Popc orn T es t

Kink / Max Slope

Field Instability at 40 Oe

Reader Induced InstabilitiesReader Instability

Writer Induced InstabilitiesWriter Induced Instabilities

(Popcorn)

ESD Soft / Hard Damage

Amplitude and

Asymmetry Degradation

Pin-Layer Reversal

No Amplitude – Hard Damage

Drive Anomaly Correlation

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0

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-300 -250 -200 -150 -100 -50 0 50 100 150 200 250 300

Transverse Transfer C u rve B ia s : 3 .9 7 8 P a r t ID : H e a d : 2

Am

plit

ud

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Forward Reverse

Amplitude variation in Drive caused by High Hysteresis shown in Transfer Curve

QST to DET CorrelationTest conditions QST-2002

Sweep: 275 Oe Measured at 250 Oe Bias Current: 5 mA

Guzik 1001 + 1701 Frequency: 5 MHz Filter: 60 MHz Bias Current: 5 mA RPM: 5400

Amplitude Correlation (Stack Level)

R2 = 0.9325

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0

500

1000

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2000

2500

0 500 1000 1500 2000 2500

QST PP AMP

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The Answer is YES, QST can screen out most common Anomalies!Drive Anomaly QST Function

Amplitude/Asymmetry Variation Transfer Curve Amplitude/Asymmetry

Baseline Shift / Popping Transfer Curve Barkhausen Jump and Hysteresis

Field Induced Instabilities (Kinks) Transfer Curve Max Slope and Field Induced Noise Test

Writer/Reader Induced Instabilities Writer/Reader Induced Noise Test

ESD Damage (Amp, Pin-Reversal, Asymmetry)

Transfer Curve Amp, Asymmetry and Slope

DET/ Drive Correlation YES

Additional Functionality of QST Testers

Static Tests of HSA components including Preamp Chip, Voice Coil, FCBA, Writer

Elevated Temperature Testing PZT Suspension Testing ESD Failure Threshold Testing

ESD Damage to GMR heads is considered one of the worst problems in Manufacturing Today

Due to sensitivity to ESD, GMR heads can be easily damaged or destroyed by the slightest ESD event caused by Humans or Machines in Manufacturing

Unfortunately, this problem is here to stay and will only get worse in near future as the ESD Failure Voltage level is inversely proportional to Arial Density

CDM (Charged Device Model) is rapidly becoming the standard for characterizing GMR head ESD Failure Thresholds

QST can characterize ESD damage by applying a controlled ESD events to GMR head

HBM: 10% Resistance Change

Sensor Damage

CDM: 100% Resistance Change

Multiple distributed melting points

What can be done about GMR head ESD Sensitivity ?

Improved design of GMR head which is less sensitive to ESD

Eliminate ESD events from Manufacturing Monitor GMR head performance after every

significant process to isolate and eliminate ESD events in Manufacturing

As Al Wallash – Maxtor would put it:

“Don’t loose your head over ESD”

Whatever you do, QST Testing can Help!

By Applying Varying Amplitude ESD Events to GMR Head, QST can easily determine heads Failure points

Amp Failure

Pin Reversal

Resistance Failure

Meltdown

Asymmetry

Failure

Direct-CDM SweepCDM Failure

Threshold at 5V

Partial Damage

QST is the Ultimate Test Solution for GMR head manufacturing QST Testing Methodology can be applied from Wafer to

HDA level testing QST Testing can screen out bad heads early in

manufacturing process QST Testing can identify which processes in

Manufacturing are ESDing your heads QST Testing is fast and inexpensive QST Testing can be done with None or Very Little

Handling on many test levels QST surpasses DET in analyzing pure GMR performance

References

[1] J.Himle, R.Cross, M.Greenwell, “Drive-Level Instabilities Correlated to Quasi-Static Field Testing”, MMM-Intermag 2001

[2] C. Moore, “A Comparison of Quasi-Static Characteristics and Failure Signatures of GMR Heads subjected to CDM and HBM ESD Events”

[3] Integral Solutions Int’l, “Quasi 97” and “QST-2002” Tester

Acknowledgements

Al Wallash – Quantum/Maxtor Mark Nichols – Quantum/Maxtor Jenny Himle - Maxtor