finite element modeling and of cantilever wafer test · 2017. 3. 26. · probing experiment factors...

Finite Element Modeling and Characterization of Cantilever Probe Tips Used in Wafer Test

Levi W. Hill1,2

Noelle L. Blaylock1

Stevan Hunter PhD1,21Brigham Young University Idaho

2ON SemiconductorThis work supported by ON Semiconductor

Probing Experiment Factors• Input factors

– 3 probe cards (Standard force, Large tips, High force)– 3 wafers (Pad Al thickness: 0.7um, 0.9um, 3.0um)– No. of probe touchdowns (1 or 2)

• Wafer stayed aligned between touches

– Chuck overdrive • 50um, 100um

• Probe mark measurements– Length of probe travel (scrub)– (Total Area) Scrub area + Prow area– Depth (Remaining Al thickness)

2Hill, Blaylock, Hunter

Probe Tip Characteristics per Card


Probe Card 1 Probe Card 2 Probe Card 3

Tip Diameter .8 mil 1.2 mil 0.8 mil

Force standard standard high

Example probe tip surfaces after use

Probing Experiment (3 wafers)


2 touch 2 mil overdriveProbe Card 11 touch 2 mil overdrive

1 touch 4 mil overdrive

2 touch 2 mil overdrive1 touch 2 mil overdrive1 touch 4 mil overdrive



1 touch 2mil overdrive

Probe Card 2

Probe Card 3

Probe Marks: 1 Touch @ 2mils OD• Standard Force Tip

• Large Tip

• High Force


0.7um Al

0.7um Al

0.7um Al

0.9um Al

0.9um Al

0.9um Al

3.0um Al

3.0um Al

3.0um Al

Probe Marks: 2 Touch @ 2mils OD


• Standard Force Tip

• Large Tip

• High Force

0.7um Al

0.7um Al

0.7um Al

0.9um Al

0.9um Al

0.9um Al

3.0um Al

3.0um Al

3.0um Al

Probe Marks: 1 Touch @ 4mils OD


• Standard Force Tip

• Large Tip

• High Force (2 touches)

0.7um Al

0.7um Al

0.7um Al

0.9um Al

0.9um Al

0.9um Al

3.0um Al

3.0um Al

3.0um Al

Pad Al Remaining, Prow Height


Remaining Al vs.Overdrive

Measured Al Pileup Vs.Overdrive

Coincident Touches, and Overdrive

• Both Length and Area increase slightly with 2nd coincident probe touch

• Both Length and Area increase significantly with increased Overdrive

Tip

Trav

el (u

m)

Mar

k A

rea

(um

2 )


Scrub length vstouch count

Scrub length vsOverdrive (mils)

Mark area vstouch count

Mark area vsOverdrive (mils)

Pad Al Thickness, and Probe Tip

• Scrub Length decreases with pad Al thickness, while Area decreases

• Larger tip doesn’t change Scrub Length, but increases the Area• High force probes increase Length and Area

Tip

Trav

el (u

m)

Mar

k A

rea

(um

2 )


Scrub length vsProbe card #

Mark area vsProbe card #

Scrub length vsPad Al Thickness

Mark area vs Pad Al Thickness

0.7um 0.9um 3.0um

0.7um 0.9um 3.0um

0.8mil 1.2mil 0.8mil, hf

0.8mil 1.2mil 0.8mil, hf

Finite Element Models of Probe Tips• Student‐created probe tip models are used to simulate the scrub motion of probing

• Experimental data above is used to check the validity of modeling

• Objective is to learn from modeling how to reduce probe mark size and probe longevity without causing pad or bondability issues

• Preliminary results follow:


Finite Element Model of Probe


Probe Model Used in These Simulations


Probe tip has a slight relief on the heel so it will continue to make contact as it slides forward on the pad surface

Material properties of W are used for the probe

Larger Tip Probe Model


Shortened tip length, as if the probe has been worn during use, with larger tip resulting

Cantilever Probe Model


Probe tip model under stress

Example finite element “mesh”

Probe Tip Models Under Stress


The bond pad’s upwards movement strains the tip, with the shank as a spring

Probe tips on Thin and Thick Pad Al


0.7um pad Al thickness 3.0um pad Al thickness

High Force Probe Tip


Low Overdrive High Overdrive

Overdrive Effect: Measure, Model


• Overdrive is easiest to model and simulate• Slope matches, but need offset adjustment in model

Measured SimulatedScrub length vs

OverdriveScrub length vs

Overdrive

Probe Tip Effect: Measure, Model


• Model has small offset but matches slope for small and large tips

• Model is off for high force tip – insufficient force applied, compared to actual probes

Measured SimulatedScrub length vs

Probe tipScrub length vs

Probe tip

0.8mil 1.2mil 0.8mil, hf0.8mil 1.2mil 0.8mil, hf

Pad Al Thk Effect: Measure, Model


• Insufficient interaction with the pad Al in the model, so the scrub length doesn’t drop enough

• Recommend more tip contact area in the model

Measured Simulated

0.7um 3.0um 0.7um 3.0um

Other Probe Models


Higher angle probe

Lower angle probe

Other Probe Models (cont)


Summary• Experiment to create various probe marks

– 3 pad Al thicknesses– 3 different probe tip conditions– 2 different overdrives– 1 and 2 touches

• Created FEM models of various probe tips• Ran simulations to attempt matching with experiment data

• Lots more work to do…


SW Test 2014 Workshop ProceedingsSW Test 2014 Corporate SupportersSW Test 2014 Program "At A Glance"SW Test 2014 ExhibitorsSW Test 2014 Technical Program OverviewMonday, June 9

Technical Program - MondayMonday, June 9, 2014Welcome to SW Test 2014Characterizing the Touchdown and the DamageFinite Element Modeling and Characterization of CantileverProbe Tips Used in Wafer TestTransverse Load Analysis for Semiconductor ApplicationsILD study contact/deprocessing methodology comparison

High Voltage, High Temperature, High CurrentCost Effective 1,000V High Voltage Parametric Test TechniqueHigh pulsed current wafer probing in high temperature conditions:comprehensive framework for vertical and cantilever probe designA Study on CCC of fine pitch vertical probe;Simplified CCC formula and its verification

Design of Advanced ProbecardsDescription of the MEMS CIS probe card - electricalcharacteristics, parallelism & probing propertiesCan testers and probe cards keep up withspeed requirements for image sensors?Improving Signal Integrity through Advanced Probe CardDesign and Probe Card MetrologyHow to extend the lifetime of your current probe card analyzer

Advanced Vertical TechnologiesConductive Paste-Based Interconnect Technologyfor High Performance Probe CardChallenges and Solutions in future designs of Vertical Probe CardsAnalysis of Design Parameters that Affect thePerformance of Multi-site Vertical Probe Cards

Characterizing the Touchdown and the DamageFinite Element Modeling and Characterization of CantileverProbe Tips Used in Wafer TestTransverse Load Analysis for Semiconductor ApplicationsILD study contact/deprocessing methodology comparison

High Voltage, High Temperature, High CurrentCost Effective 1,000V High Voltage Parametric Test TechniqueHigh pulsed current wafer probing in high temperature conditions:comprehensive framework for vertical and cantilever probe designA Study on CCC of fine pitch vertical probe;Simplified CCC formula and its verification

Design of Advanced ProbecardsDescription of the MEMS CIS probe card ‐ electricalcharacteristics, parallelism & probing propertiesCan testers and probe cards keep up withspeed requirements for image sensors?Improving Signal Integrity through Advanced Probe CardDesign and Probe Card MetrologyHow to extend the lifetime of your current probe card analyzer

Advanced Vertical TechnologiesConductive Paste‐Based Interconnect Technologyfor High Performance Probe CardChallenges and Solutions in future designs of Vertical Probe CardsAnalysis of Design Parameters that Affect thePerformance of Multi‐site Vertical Probe Cards

42 Full-size ExhibitsSave the Date - June 7 to 10, 2015

finite element modeling and of cantilever wafer test · 2017. 3. 26. · probing experiment factors...

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