Electrical Planarity Characterization of High Parallelism

John CaldwellMicron Technology, Inc.

Electrical Planarity Electrical Planarity Characterization of High Characterization of High Parallelism Probe CardsParallelism Probe Cards

June 8June 8--11, 200811, 2008San Diego, CA USASan Diego, CA USA

June 8 to 11, 2008June 8 to 11, 2008June 8 to 11, 2008 IEEE SW Test WorkshopIEEE SW Test WorkshopIEEE SW Test Workshop 222

IntroductionIntroduction• Challenge

– High parallelism (1TD 300mm)– Thermal deflection– High probe count– Shrinking bond pads

• Can we maintain the same probe card planarity specification as 32x to 64x parallelism five years ago??– Yes!

• Micron has employed techniques for analyzing optical and electrical planarity data; resulting in…– Improved test cell performance– Better understanding of high parallelism probe card planarity

characteristics– Correlation between metrology and test cell tools


Introduction (2)Introduction (2)• Optical versus electrical… Or, optical +

electrical?– Optical + electrical

• Electrical first-to-last (EF2L) provides information on potential variance components within the test cell– Probe card planarity and tilt– Prober chuck curvature, tilt, or deflection– System deflection

• Proper analysis of EF2L data allows the user to minimize test cell variance components to achieve the best possible planarity


TopicsTopics• Pitch and roll• EF2L Sequence• EF2L Examples

1. %Contact by delta-Z2. System-to-system planarity & tilt comparison3. Test cell stack-up error correction4. Optical-to-electrical planarity correlation5. Probe card technology benchmark

• Summary


Pitch and Roll


Pitch and RollPitch and Roll• Pitch and roll is. . .

– A metric that represents probe card tilt when installed in metrology systems and/or test cells

– A relative comparison from one system to another when characterizing the same probe card

– Estimated by best-fit linear plane and represented in terms of µRadians

– Not a metric that was invented by Micron or used exclusively by Micron (data analysis methods vary)


Within Planarity vs. TiltWithin Planarity vs. Tilt

Radius = 295000µm

mPlanarityWithin μδ )_(

mradmTilt RadiusRollPitch μμμδ ⋅≈ )()( &


µµRadians to Radians to µµmm

05

10152025

303540

4550

0 10 20 30 40 50 60 70 80 90 100

110

120

130

140

150

r = 295,000um (300mm 1TD)r = 150,000um

µRadians

Prob

e C

ard

Tilt

(µm

)

Slide 10 of conference proceedings


Estimating Pitch and RollEstimating Pitch and Roll

Range = 42µm

-300000

-250000

-200000

-150000

-100000

-50000

0

Y

-150000 -100000 -50000 0 50000 100000 150000 200000

X

0 10 20 30 40

100.0%99.5%97.5%90.0%75.0%50.0%25.0%10.0%2.5%0.5%0.0%

maximum

quartilemedianquartile

minimum

42.00042.00038.62528.50021.00018.000

9.0006.0006.0002.4750.000

Quantiles

Planarity (um)

Pitch = -7µrad Roll = 73.4µrad R2 = 0.36

0

10

20

30

40

50

-1.5e+5

-1.0e+5

-5.0e+4

0.0

5.0e+4

1.0e+5

1.5e+5

2.0e+5 -3e+5

-3e+5

-2e+5

-2e+5

-1e+5

-5e+4

0Ele

ctri

cal

Pla

nari

ty (

um

)

X (Prober Front)

Y

TILT


Residual Plot (Within Planarity)Residual Plot (Within Planarity)

-15 -5 0 5 10 15 20

100.0%99.5%97.5%90.0%75.0%50.0%25.0%10.0%2.5%0.5%0.0%

maximum

quartilemedianquartile

minimum

22.2620.7017.1210.18

3.14-0.53-5.26-7.83

-11.14-12.83-12.94

Quantiles

Linear Fit Residuals (um)

-300000

-250000

-200000

-150000

-100000

-50000

0

Y

-150000 -100000 -50000 0 50000 100000 150000 200000

X

Range = 35µm

Pitch = 2.5µradRoll = 1.5µrad

-20

-10

0

10

20

30

-1e+5

0

1e+5

2e+5 -3e+5

-2e+5

-1e+5

0

Ele

ctri

cal P

lan

ari

ty (

um

)

X (Prober Front)

Y

MIN TILT


~73~73µµrad Doesnrad Doesn’’t t ReallyReally AddAdd ~21~21µµm To Planarity Windowm To Planarity Window

-40

-20

0

20

40

60

-2e+5-2e+5-1e+5-5e+405e+41e+5

-3e+5 -2e+5 -1e+5 0

Z D

ata

X D

ata

Y Data

mmTilt

mradmTilt

mradmTilt RadiusRollPitch

μμ

μμμ

μμμ

δ

δ

δ

7.21

000,2954.73

&

)(

)(

)()(

≈

⋅≈

⋅≈



-40

-20

0

20

40

60

-2e+5-2e+5-1e+5-5e+405e+41e+5

-3e+5 -2e+5 -1e+5 0

Z D

ata

X D

ata

Y Data

mmPlanarityWithin μδ

μ42)_( =



-40

-20

0

20

40

60

-2e+5-2e+5-1e+5-5e+405e+41e+5

-3e+5 -2e+5 -1e+5 0

Z D

ata

X D

ata

Y Data

mmPlanarityWithin μδ

μ35)_( =


EF2L Sequence


EF2L SequenceEF2L Sequence


EF2L Examples


Example: %pass DataExample: %pass Datadelta-Z #PASS DELTA-PASS %PASS

0 6 6 0.2%

3 12 6 0.4%

6 18 6 0.6%

9 28 10 0.9%

12 146 118 4.8%

15 443 297 14.6%

18 695 252 23.0%

21 1403 708 46.4%

24 2016 613 66.7%

27 2315 299 76.6%

30 2720 405 89.9%

33 2914 194 96.4%

36 2953 39 97.7%

39 2967 14 98.1%


0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51

0:00:00

0:07:14

0:58:10

1:16:12

1:49:41

%pass by delta%pass by delta--ZZ

deltadelta--ZZ

%pas

s%p

ass

Soak Soak TimeTime


Example: Pin HeightExample: Pin HeightTESTER DUT X-COORD

(um)Y-COORD

(um) PROBE# PIN_HEIGHT (um)

0 -59903 -235432 1 15

0 -59903 -235432 2 18

0 -59903 -235432 3 18

0 -59903 -235432 4 15

0 -59903 -235432 5 18

0 -59903 -235432 6 18

0 -59903 -235432 7 15

… … … … …

… … … … …


SystemSystem--toto--System Planarity CorrelationSystem Planarity Correlation

-200000

-100000

0

Y

-100000 0 100000

X

-200000

-100000

0

Y

-100000 0 100000

X

-200000

-100000

0

Y

-100000 0 100000

X

-200000

-100000

0

Y

-100000 0 100000

X

TSTR1 TSTR2

TSTR3 TSTR4

Legend

Pin Height (um)<= 0.000<= 5.833<= 11.667<= 17.500<= 23.333<= 29.167<= 35.000> 35.000

Problem Test Cell


Test Cell Problem ResolutionTest Cell Problem Resolution

• Planarity signature: Inverted bowl

• Root cause: Prober chuck curvature

• Solution: Replaced prober chuck

<=-35um<=-15um

0um

Prober Chuck Profile

-200000

-100000

0

Y

-100000 0 100000

XTSTR4


SystemSystem--toto--System Tilt CorrelationSystem Tilt Correlation

Best Fit Linear Plane

TSTR1 TSTR2 TSTR3 TSTR4

TSTR1 TSTR2 TSTR3 TSTR4 Range

Pitch (µrad) 41 42 53 5 48

Roll (µrad) 30 5 44 24 39


OpticalOptical--toto--Electrical CorrelationElectrical Correlation

-300000

-250000

-200000

-150000

-100000

-50000

0

Y

-200000 -150000 -100000 -50000 0 50000 100000

X

-200000

-100000

0

Y

-100000 0 100000

X

Electrical (EF2L)

Legend

Pin Height (um)<= 0.000<= 5.833<= 11.667<= 17.500<= 23.333<= 29.167<= 35.000> 35.000

Pitch (µrad) 49

Roll (µrad) 13

Pitch (µrad) 54

Roll (µrad) 45

Optical (PTPA)


Probe Card Technology BenchmarkProbe Card Technology Benchmark

Legend

Pin Height (um)<= 0.000<= 5.833<= 11.667<= 17.500<= 23.333<= 29.167<= 35.000> 35.000

-300000

-200000

-100000

0

Y

-100000 0 100000

X

-300000

-200000

-100000

0

Y

-100000 0 100000

X

Technology

- A

Excellent Planarity Planarity Out Of Spec

*Both probe cards 1TD 300mm

Technology

- B


• Meeting the challenge– High parallelism (1TD 300mm)– Thermal deflection– High probe count– Shrinking bond pads

• EF2L is a key component in understanding probe card planarity– Electrical planarity spec validation– System-to-system correlation– Probe card technology benchmark– Thermal profile / soak– Identify other test cell issues, such as prober chuck curvature and

system deflection

SummarySummary


Thank You!Thank You!

Electrical Planarity Characterization of High Parallelism

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