Advanced Microelectronic Probing Solutions M I C R O T E C HCASCADE TM

Achieving Low Contact Resistance onAluminum Using Pyramid Probe Tips with

MicroscrubTM Technology

Ken Smith, Cascade MicrotechSWTW 1999

Pyramid Probe’s New Facility (Formerly Etec Building)

Advanced Microelectronic Probing Solutions M I C R O T E C HCASCADE TM

Outline

1. Industry Requirements

2. Microscrub Technology Operation

3. Current Implementation

4. Sematech/Sandia Evaluation

5. Lucent Evaluation

6. Intel Evaluation

7. Summary

Advanced Microelectronic Probing Solutions M I C R O T E C HCASCADE TM

Industry Requirements

● Contact resistance reliably less than 1.0ohm

● Minimize pad damage● Minimize scrub for small bond pads and

fine pitch● Minimal cleaning and maintenance● DESIGN REQUIREMENT: Uniform scrub

independent of position on the probe

Advanced Microelectronic Probing Solutions M I C R O T E C HCASCADE TM

Microscrub Tip with Integral Beam

Advanced Microelectronic Probing Solutions M I C R O T E C HCASCADE TM

Microscrub Principles of Operation

● Integral beam

● Offset forces

● Compliant backing

● Rotational moment

● Uniform scrub for all probe tips

Advanced Microelectronic Probing Solutions M I C R O T E C HCASCADE TM

Initial Microscrub Implementation(1996)

Advanced Microelectronic Probing Solutions M I C R O T E C HCASCADE TM

Typical Initial Contact ResistanceResults (1996)

Contact Resistance during Life Test

00.050.1

0.150.2

0.250.3

0.350.4

0.450.5

1460

00

1560

00

1660

00

1760

00

1860

00

1960

00

2060

00

2160

00

2260

00

2360

00

2460

00

2560

00

Minimum

Maximum

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Current Microscrub Implementation(1998)

● Smaller tips (30 >> 15 microns)● Taller tips (30 >> 60 microns)● Less probe force (20 >> 10 grams)● Engineering DOE parameters:

– Independent variables: Beam length,thickness, tip height, tip diameter,elastomer durometer, thickness, force pertip

– Indicators: Contact resistance,compliance, interaction with wafercontamination

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Pyramid Probe Tips with MEMsProcess

9 M I C R O T E C HCASCADETM

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Evaluation at Sandia

● Same set up as SWTW ‘98 Sematechcantilever probe data

– Three point Kelvin– HP 4062– EG 4090– Sematech funded facility

● No cleaning

● Stepped off wafer multiple times

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Pyramid Probe Contact Resistancefrom Sandia Lifetest (@ 85 C)

Lifetest at Sandia on a blank aluminum wafer

0 10 20 30 40 50 60 70 80

90 100

110120

160

170

180

190200

210

220230

240

250260

270

280

320

330

340

350360

370

380

390

400410

420

430440

Touchdowns (x 1000)(box plot without tails comparative to data shown at SWTW '98

page 24)

0

0.5

1

1.5

2

2.5

3

Resistance (contact + signal line) (ohm

s)

(5 mil overtravel at 85 C)

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Conventional Cantilever Probe CardContact Resistance (@ 85 C)

SEMATECH Applied Precision, Inc.Advanced Probing Systems, Inc. Sandia National LabsSWTW ‘98

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Comparison of Cantilever (@ 30 C) vs.Pyramid (@ 85 C)

Lifetest at Sandia on a blank aluminum wafer

0 10 20 30 40 50 60 70 80

90 100

110120

160

170

180

190200

210

220230

240

250260

270

280

320

330

340

350360

370

380

390

400410

420

430440

Touchdowns (x 1000)(box plot without tails comparative to data shown at SWTW '98

page 24)

0

0.5

1

1.5

2

2.5

3

Resistance (contact + signal line) (ohm

s)

(5 mil overtravel at 85 C)

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Lucent Evaluation: 200K Cycles WithNo Cleaning

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0TD

2KTD

13KTD

24KTD

35KTD

46KTD

46KIN

IT56

KTD67

KTD82

KTD11

1K13

3K17

7K21

0K

loop res AVGcres STDDEV

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Typical Pyramid Probe and Cantilever Marks

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Single Pyramid Mark SEM

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One Cantilever, Two Pyramid Scrub Marks

1

21

41

61

81

S1S8

S15

S22

S29

S36

S43

S50

S57

S64

S71

S78

S85

S92

S99

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

Z - height (microns)

X - one division = one micron

Y - one division = one micron

One Cantilever and two Pyramid Probe scrub marks from Sandia Labs test wafer

2.5-32-2.51.5-21-1.50.5-10-0.5-0.5-0-1--0.5-1.5--1

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Intel Multi-DUT FlashRAM

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Multi-DUT Testing of FlashRAM

● 2 X 5 Multi-DUTprobe layout forFlashRam devices

● 500 I/O● 25 mm square

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Standard Internal Infant Lifetest

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

1 70 139 208 277 346 415 484 553 622 691 760 829 898 967 1036

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Acknowledgements

● NIST/ATP, DARPA, Sandia Labs,Sematech

● Rey Rincon, Phil Seitzer, DaveUnzicker, Khe Ting

● About 30 Cascade team members

Advanced Microelectronic Probing Solutions M I C R O T E C HCASCADE TM

Summary

● This is the first time Membrane probes havepublished excellent contact resistance and lifetest results on aluminum

● Small contacts and small scrub distancedrastically reduce pad damage and allow smallerpads

● Uniformly engineered consistent Microscrub isthe magic that makes it work

● Microscrub contact structure is compatible withfine pitch, array, multitest and high frequencyapplications