SWTW 2004

Celerity ResearchCelerity Research

Probe and Planarize™ --Optimizing Bump Shape and Height at Probe

Vada Dean and Tom NguyenSouthwest Test Workshop 2004

2 SWTW 2004

OverviewOverview

• The Problem -- Flip Chip Device Reliability

• The Solution -- Probe and Planarize™

• Smart PnP Technology™

SWTW 2004

The ProblemThe Problem

Flip Chip Device Reliability

4 SWTW 2004

Flip Chip Device Reliability IssuesFlip Chip Device Reliability Issues

• Probe marks damage bumps on the wafer

• Scratched and penetrated bumps trap contamination and flux

• Bump reflow adds yield risk and cost

• Height variation of wafer bumps hinder interconnect formation

5 SWTW 2004

Bump Damage, ContaminationBump Damage, Contaminationand Reflowand Reflow

Eutectic60 µ OT

Hi Lead60 µ OT

Cu Pillar60 µ OT

Additional Temp Excursion causes:• PMOS transistor damage• Die Yield Loss• Reduced Final Test Yield• Additional $’s for wafer reflow

process

REFLOW WAFER TO ELIMINATE SOLDER DAMAGE (260°C)

• Trapped contaminants and flux weaken flip chip interconnect joints

• Increases variation of bump height

6 SWTW 2004

Typical Bump Height DistributionTypical Bump Height Distribution

12

71

178

381

752

10791124

849

496

232

9449

25 14 6 3 4 1 0 2 1 1 1 0 0 0 0 0 0 1

113 115 117 119 121 123 125 127 128 131 133 135 137 139 141

Chip

Substrate

Ball Height (microns)Avg. = 118.77, Sigma = 2.10, Number Balls = 5376

7 SWTW 2004

Weak Flip Chip InterconnectWeak Flip Chip Interconnect

Inferior Interconnect and Lack of Wetting:• Smaller ball with little or no contact after reflow• Contamination interference

SWTW 2004

The SolutionThe Solution

Probe and Planarize™

9 SWTW 2004

Smart PnP ProbeSmart PnP Probe™™with Probe and with Probe and PlanarizePlanarize™™

Advantages• Reduced variation of bump height

enhances interconnect integrity• Flat surface eliminates trapped

contamination and flux• Textured surface improves reflow

and wetting

Probe and Planarize™ uniformly deforms bumps across the wafer

10 SWTW 2004

Smart PnP ProbeSmart PnP Probe™™Improves Bump Height DistributionImproves Bump Height Distribution

2

10

36

83

61

37

11

4

20

2523 22

32

74

30

8

2

0

10

20

30

40

50

60

70

80

90

100

70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95

Bump Heights (um)

Freq

uenc

y of

Occ

uran

ce

Post-test Avg=76.4um, Sigma=1.17um Pre-test Avg=86.7um, Sigma=2.07um

Distribution Shiftafter Probe and Planarize™

Wafers received from fab have significant bump height variation

Bump height distribution is unpredictable

11 SWTW 2004

Probe & Probe & PlanarizePlanarizeTMTM ResultsResults

Unitive Bump Heights DistrubutionPre-Probe vs. Post-Probe

0

10

20

30

40

50

60

70

80

90

100

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125

Bump Heights (um)

Freq

uenc

y of

Occ

uran

ce

Post-Probe[Avg, Stdev]= 102.28, 1.46 Pre-Probe [Avg, Stdev]= 116.40, 2.94

BeforeAvg. Bump Ht. = 116.40Std. Dev. = 2.94

After Probe & Planarize™Avg. Bump Ht. = 102.28Std. Dev. = 1.46

Vendor A

Lot # 2

High Pb

Celerity Research Bump

Fab

Unitive Bump Heights DistrubutionPre-Probe vs. Post-Probe

0

10

20

30

40

50

60

70

80

90

100

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125

Bump Heights (um)

Freq

uenc

y of

Occ

uran

ce

Post-Probe[Avg, Stdev]= 96.92, 1.68 Pre-Probe [Avg, Stdev]= 109.96, 2.42

BeforeAvg. Bump Ht. = 109.96Std. Dev. = 2.42

After Probe & Planarize™Avg. Bump Ht. = 99.92Std. Dev. = 1.68

Vendor A

Lot # 4

High Pb

Celerity Research Bump

Fab

BeforeAvg. Bump Ht. = 111.16Std. Dev. = 4.58

After Probe & Planarize™Avg. Bump Ht. = 88.24Std. Dev. = 1.13

Unitive Bump Heights DistrubutionPre-Probe vs. Post-Probe

0

10

20

30

40

50

60

70

80

90

100

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125

Bump Heights (um)

Freq

uenc

y of

Occ

uran

ce

Post-Probe[Avg, Stdev]= 88.24, 1.13 Pre-Probe [Avg, Stdev]= 111.16, 4.58

Vendor A

Lot # 3

High Pb

Celerity Research

Bump Fab

12 SWTW 2004

Probe and Probe and PlanarizePlanarize™™ Improves ReliabilityImproves Reliability

Non-PlanarizedBump Structure Weak flip chip

interconnect joint. Will result in reliability failure

of device.

Probe and Planarize™Bump Structure

Preferred flip chip interconnect joint

structure.

13 SWTW 2004

0/500/500/500/500/500/50HTS 165C 500 hrs

0/500/500/500/500/500/50UB-Hast 168 hrs

0/1500/1500/1500/1500/1500/150UB-Hast 96 hrs

11/2500/25019/2500/2508/2500/250TC-B 3000 cycles

52/1000/10057/1000/10011/1000/100TC-B 4500 cycles

0/6000/6000/6000/6000/6000/600MSL L3

ControlPnPControlPnPControlPnP

High PbEutecticCu Pillar

Smart PnP ProbesSmart PnP Probes™™ Reliability StudyReliability Study

MTBS Daisy Chain (15 x 15 mm die size, Var. pitch 125–240µ)TF-Polyimide 31 x 31 mm FC-BGA PackageASE-M / MTBS FC-BGA Assembly Process

SWTW 2004

Smart PnP TechnologySmart PnP Technology™™

15 SWTW 2004

Celerity Research Smart PnP ProbeCelerity Research Smart PnP Probe™™

• Smart PnP Probe™ with unique Probe and Planarize™ technology:• High density capability (up to

10000 pins)• Fine pitch (60 micron or less)• Massively parallel• Superior electrical performance• The only probe technology that

improves the integrity of the flip chip joint interconnect

16 SWTW 2004

Smart PnP ProbesSmart PnP Probes™™

Smart PnP Probes™X-Section

Smart PnP Probes™height variance < 2 µ

• Coplanarity <+/- 2µ.

• Rigid and durable probes

17 SWTW 2004

Smart PnP ProbeSmart PnP Probe™™ PlanarityPlanarity

Coplanarity240 Probes Monitored -- Camtek Falcon

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 0.5k 1k 5k 10k 50k 100k 500k

Touchdowns

Plan

arity

(um

)

18 SWTW 2004

Smart ProbeSmart Probe TechnologyTechnology™™Utilizes Advanced Design and SimulationUtilizes Advanced Design and Simulation

• Electrical parasitics well defined and modeled with EDA tools and simulators

• Lumped elements can be designed into the Smart PnP Probe™

19 SWTW 2004

DataIn Pins - Diff TDR/TDT response for 25ps input

Output risetime is 27psSkew is less than 0.25ps

PnP ProbePnP Probe™™ TDR/TDTTDR/TDT

20 SWTW 2004

• DataIn PinsEye-diagram at 10 Gb/sec

• Jitter is less than 1ps

• Eye-closure is 6%(measured 30ps after zero crossing)

Smart PnP ProbeSmart PnP Probe™™ Eye DiagramEye Diagram

21 SWTW 2004

Smart PnP ProbeSmart PnP Probe™™ Current CapacityCurrent Capacity

Probe Current Carrying Capacity20 microns overtravel

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00 900.00

Curent (mA)

Prob

e Fo

rce

(g)

22 SWTW 2004

Contact Resistance PerformanceContact Resistance Performance

Change in Contact Resistance240 Probes Monitored

-0.5000

-0.4000

-0.3000

-0.2000

-0.1000

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.5k 1k 5k 10k 50k 100k 500k

Touchdowns

Res

ista

nce

(ohm

s)

Wafers tested using Accretech UF200S Proberand Standard Tester Configuration

23 SWTW 2004

Smart PnP ProbeSmart PnP Probe™™Probes After 500k Touchdowns (no clean)Probes After 500k Touchdowns (no clean)

Smart PnP Probe™

Before Touchdown

Smart PnP Probe™

After 500K Touchdowns

24 SWTW 2004

ConclusionsConclusions

• Probe and Planarize™• Optimizes Bump Shape and Height at Probe• Improves Flip-Chip Device Reliability

• Smart PnP Technology™• Provides superior coplanarity• Maintains advanced electrical performance throughout life

of probe card• Provides reproducible low Cres

• Enables fine pitch and massive parallel testing

25 SWTW 2004

AcknowledgementsAcknowledgements

Chainarong Asanasavest -- Celerity Research Director of TechnologyDave Brown -- Celerity Research Design ManagerRandy Chau -- Celerity Research Application EngineerRomi Pradhan -- Accretech Product Manager

This presentation would not have been possible without the support and equipment provided by Accretech, Camtek, and Gigatest